fix: security hardening — 40 findings from full codebase review

Full codebase review by 4 independent agents (security, architecture,
code quality, correctness) identified ~80 findings. This commit fixes 40
of them across all workspace crates.

Critical fixes:
- Federation service: validate origin against mTLS cert CN/SAN (C1)
- WS bridge: add DM channel auth, size limits, rate limiting (C2)
- hpke_seal: panic on error instead of silent empty ciphertext (C3)
- hpke_setup_sender_and_export: error on parse fail, no PQ downgrade (C7)

Security fixes:
- Zeroize: seed_bytes() returns Zeroizing<[u8;32]>, private_to_bytes()
  returns Zeroizing<Vec<u8>>, ClientAuth.access_token, SessionState.password,
  conversation hex_key all wrapped in Zeroizing
- Keystore: 0o600 file permissions on Unix
- MeshIdentity: 0o600 file permissions on Unix
- Timing floors: resolveIdentity + WS bridge resolve_user get 5ms floor
- Mobile: TLS verification gated behind insecure-dev feature flag
- Proto: from_bytes default limit tightened from 64 MiB to 8 MiB

Correctness fixes:
- fetch_wait: register waiter before fetch to close TOCTOU window
- MeshEnvelope: exclude hop_count from signature (forwarding no longer
  invalidates sender signature)
- BroadcastChannel: encrypt returns Result instead of panicking
- transcript: rename verify_transcript_chain → validate_transcript_structure
- group.rs: extract shared process_incoming() for receive_message variants
- auth_ops: remove spurious RegistrationRequest deserialization
- MeshStore.seen: bounded to 100K with FIFO eviction

Quality fixes:
- FFI error classification: typed downcast instead of string matching
- Plugin HookVTable: SAFETY documentation for unsafe Send+Sync
- clippy::unwrap_used: warn → deny workspace-wide
- Various .unwrap_or("") → proper error returns

Review report: docs/REVIEW-2026-03-04.md
152 tests passing (72 core + 35 server + 14 E2E + 1 doctest + 30 P2P)

Cargo.lock

@@ -224,6 +224,45 @@ version = "0.7.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "7c02d123df017efcdfbd739ef81735b36c5ba83ec3c59c80a9d7ecc718f92e50"
 
+[[package]]
+name = "asn1-rs"
+version = "0.6.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5493c3bedbacf7fd7382c6346bbd66687d12bbaad3a89a2d2c303ee6cf20b048"
+dependencies = [
+ "asn1-rs-derive",
+ "asn1-rs-impl",
+ "displaydoc",
+ "nom",
+ "num-traits",
+ "rusticata-macros",
+ "thiserror 1.0.69",
+ "time",
+]
+
+[[package]]
+name = "asn1-rs-derive"
+version = "0.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "965c2d33e53cb6b267e148a4cb0760bc01f4904c1cd4bb4002a085bb016d1490"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.117",
+ "synstructure",
+]
+
+[[package]]
+name = "asn1-rs-impl"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7b18050c2cd6fe86c3a76584ef5e0baf286d038cda203eb6223df2cc413565f7"
+dependencies = [
+ "proc-macro2",
+ "quote",
+ "syn 2.0.117",
+]
+
 [[package]]
 name = "assert_cmd"
 version = "2.1.2"
@@ -1456,6 +1495,20 @@ dependencies = [
  "zeroize",
 ]
 
+[[package]]
+name = "der-parser"
+version = "9.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5cd0a5c643689626bec213c4d8bd4d96acc8ffdb4ad4bb6bc16abf27d5f4b553"
+dependencies = [
+ "asn1-rs",
+ "displaydoc",
+ "nom",
+ "num-bigint",
+ "num-traits",
+ "rusticata-macros",
+]
+
 [[package]]
 name = "deranged"
 version = "0.5.8"
@@ -2940,7 +2993,7 @@ dependencies = [
  "tokio",
  "tokio-rustls",
  "tower-service",
- "webpki-roots",
+ "webpki-roots 1.0.6",
 ]
 
 [[package]]
@@ -3292,7 +3345,7 @@ dependencies = [
  "tracing",
  "url",
  "wasm-bindgen-futures",
- "webpki-roots",
+ "webpki-roots 1.0.6",
 ]
 
 [[package]]
@@ -3444,7 +3497,7 @@ dependencies = [
  "tracing",
  "url",
  "vergen-gitcl",
- "webpki-roots",
+ "webpki-roots 1.0.6",
  "ws_stream_wasm",
  "z32",
 ]
@@ -3935,6 +3988,12 @@ version = "0.3.17"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6877bb514081ee2a7ff5ef9de3281f14a4dd4bceac4c09388074a6b5df8a139a"
 
+[[package]]
+name = "minimal-lexical"
+version = "0.2.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "68354c5c6bd36d73ff3feceb05efa59b6acb7626617f4962be322a825e61f79a"
+
 [[package]]
 name = "miniz_oxide"
 version = "0.8.9"
@@ -4220,6 +4279,16 @@ version = "0.1.14"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "72ef4a56884ca558e5ddb05a1d1e7e1bfd9a68d9ed024c21704cc98872dae1bb"
 
+[[package]]
+name = "nom"
+version = "7.1.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d273983c5a657a70a3e8f2a01329822f3b8c8172b73826411a55751e404a0a4a"
+dependencies = [
+ "memchr",
+ "minimal-lexical",
+]
+
 [[package]]
 name = "ntimestamp"
 version = "1.0.0"
@@ -4244,12 +4313,31 @@ dependencies = [
  "windows-sys 0.61.2",
 ]
 
+[[package]]
+name = "num-bigint"
+version = "0.4.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a5e44f723f1133c9deac646763579fdb3ac745e418f2a7af9cd0c431da1f20b9"
+dependencies = [
+ "num-integer",
+ "num-traits",
+]
+
 [[package]]
 name = "num-conv"
 version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "cf97ec579c3c42f953ef76dbf8d55ac91fb219dde70e49aa4a6b7d74e9919050"
 
+[[package]]
+name = "num-integer"
+version = "0.1.46"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7969661fd2958a5cb096e56c8e1ad0444ac2bbcd0061bd28660485a44879858f"
+dependencies = [
+ "num-traits",
+]
+
 [[package]]
 name = "num-traits"
 version = "0.2.19"
@@ -4537,6 +4625,15 @@ dependencies = [
  "memchr",
 ]
 
+[[package]]
+name = "oid-registry"
+version = "0.7.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "a8d8034d9489cdaf79228eb9f6a3b8d7bb32ba00d6645ebd48eef4077ceb5bd9"
+dependencies = [
+ "asn1-rs",
+]
+
 [[package]]
 name = "once_cell"
 version = "1.21.3"
@@ -5460,6 +5557,7 @@ dependencies = [
  "rustls",
  "serde",
  "serde_json",
+ "serde_yaml",
  "sha2 0.10.9",
  "tempfile",
  "thiserror 1.0.69",
@@ -5507,6 +5605,7 @@ name = "quicproquo-ffi"
 version = "0.1.0"
 dependencies = [
  "anyhow",
+ "capnp",
  "hex",
  "quicproquo-client",
  "serde_json",
@@ -5553,6 +5652,7 @@ dependencies = [
  "rcgen",
  "rustls",
  "tokio",
+ "webpki-roots 0.26.11",
 ]
 
 [[package]]
@@ -5571,6 +5671,7 @@ dependencies = [
  "tempfile",
  "tokio",
  "tracing",
+ "zeroize",
 ]
 
 [[package]]
@@ -5590,6 +5691,7 @@ name = "quicproquo-server"
 version = "0.1.0"
 dependencies = [
  "anyhow",
+ "base64 0.22.1",
  "bincode",
  "capnp",
  "capnp-rpc",
@@ -5619,10 +5721,12 @@ dependencies = [
  "tempfile",
  "thiserror 1.0.69",
  "tokio",
+ "tokio-tungstenite",
  "tokio-util",
  "toml 0.8.23",
  "tracing",
  "tracing-subscriber",
+ "x509-parser",
  "zeroize",
 ]
 
@@ -5985,7 +6089,7 @@ dependencies = [
  "wasm-bindgen-futures",
  "wasm-streams 0.4.2",
  "web-sys",
- "webpki-roots",
+ "webpki-roots 1.0.6",
 ]
 
 [[package]]
@@ -6103,6 +6207,15 @@ dependencies = [
  "semver",
 ]
 
+[[package]]
+name = "rusticata-macros"
+version = "4.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "faf0c4a6ece9950b9abdb62b1cfcf2a68b3b67a10ba445b3bb85be2a293d0632"
+dependencies = [
+ "nom",
+]
+
 [[package]]
 name = "rustix"
 version = "0.38.44"
@@ -6535,6 +6648,19 @@ dependencies = [
  "syn 2.0.117",
 ]
 
+[[package]]
+name = "serde_yaml"
+version = "0.9.34+deprecated"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6a8b1a1a2ebf674015cc02edccce75287f1a0130d394307b36743c2f5d504b47"
+dependencies = [
+ "indexmap 2.13.0",
+ "itoa",
+ "ryu",
+ "serde",
+ "unsafe-libyaml",
+]
+
 [[package]]
 name = "serdect"
 version = "0.2.0"
@@ -6577,6 +6703,17 @@ dependencies = [
  "stable_deref_trait",
 ]
 
+[[package]]
+name = "sha1"
+version = "0.10.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e3bf829a2d51ab4a5ddf1352d8470c140cadc8301b2ae1789db023f01cedd6ba"
+dependencies = [
+ "cfg-if",
+ "cpufeatures",
+ "digest 0.10.7",
+]
+
 [[package]]
 name = "sha1_smol"
 version = "1.0.1"
@@ -7550,6 +7687,18 @@ dependencies = [
  "tokio-util",
 ]
 
+[[package]]
+name = "tokio-tungstenite"
+version = "0.26.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "7a9daff607c6d2bf6c16fd681ccb7eecc83e4e2cdc1ca067ffaadfca5de7f084"
+dependencies = [
+ "futures-util",
+ "log",
+ "tokio",
+ "tungstenite",
+]
+
 [[package]]
 name = "tokio-util"
 version = "0.7.18"
@@ -7836,6 +7985,23 @@ version = "0.2.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e421abadd41a4225275504ea4d6566923418b7f05506fbc9c0fe86ba7396114b"
 
+[[package]]
+name = "tungstenite"
+version = "0.26.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4793cb5e56680ecbb1d843515b23b6de9a75eb04b66643e256a396d43be33c13"
+dependencies = [
+ "bytes",
+ "data-encoding",
+ "http",
+ "httparse",
+ "log",
+ "rand 0.9.2",
+ "sha1",
+ "thiserror 2.0.18",
+ "utf-8",
+]
+
 [[package]]
 name = "typeid"
 version = "1.0.3"
@@ -7950,6 +8116,12 @@ dependencies = [
  "subtle",
 ]
 
+[[package]]
+name = "unsafe-libyaml"
+version = "0.2.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "673aac59facbab8a9007c7f6108d11f63b603f7cabff99fabf650fea5c32b861"
+
 [[package]]
 name = "untrusted"
 version = "0.9.0"
@@ -8372,6 +8544,15 @@ dependencies = [
  "rustls-pki-types",
 ]
 
+[[package]]
+name = "webpki-roots"
+version = "0.26.11"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "521bc38abb08001b01866da9f51eb7c5d647a19260e00054a8c7fd5f9e57f7a9"
+dependencies = [
+ "webpki-roots 1.0.6",
+]
+
 [[package]]
 name = "webpki-roots"
 version = "1.0.6"
@@ -9230,6 +9411,23 @@ dependencies = [
  "zeroize",
 ]
 
+[[package]]
+name = "x509-parser"
+version = "0.16.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "fcbc162f30700d6f3f82a24bf7cc62ffe7caea42c0b2cba8bf7f3ae50cf51f69"
+dependencies = [
+ "asn1-rs",
+ "data-encoding",
+ "der-parser",
+ "lazy_static",
+ "nom",
+ "oid-registry",
+ "rusticata-macros",
+ "thiserror 1.0.69",
+ "time",
+]
+
 [[package]]
 name = "xml-rs"
 version = "0.8.28"