chore: rename project quicnprotochat -> quicproquo (binaries: qpq)

Rename the entire workspace:
- Crate packages: quicnprotochat-{core,proto,server,client,gui,p2p,mobile} -> quicproquo-*
- Binary names: quicnprotochat -> qpq, quicnprotochat-server -> qpq-server,
  quicnprotochat-gui -> qpq-gui
- Default files: *-state.bin -> qpq-state.bin, *-server.toml -> qpq-server.toml,
  *.db -> qpq.db
- Environment variable prefix: QUICNPROTOCHAT_* -> QPQ_*
- App identifier: chat.quicnproto.gui -> chat.quicproquo.gui
- Proto package: quicnprotochat.bench -> quicproquo.bench
- All documentation, Docker, CI, and script references updated

HKDF domain-separation strings and P2P ALPN remain unchanged for
backward compatibility with existing encrypted state and wire protocol.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

crates/quicproquo-core/Cargo.toml

@@ -0,0 +1,59 @@
+[package]
+name        = "quicproquo-core"
+version     = "0.1.0"
+edition     = "2021"
+description = "Crypto primitives, MLS state machine, and hybrid post-quantum KEM for quicproquo."
+license     = "MIT"
+
+[dependencies]
+# Crypto — classical
+x25519-dalek        = { workspace = true }
+ed25519-dalek       = { workspace = true }
+sha2                = { workspace = true }
+hkdf                = { workspace = true }
+chacha20poly1305    = { workspace = true }
+zeroize             = { workspace = true }
+rand                = { workspace = true }
+
+# Crypto — post-quantum hybrid KEM (M7)
+ml-kem              = { workspace = true }
+
+# Crypto — OPAQUE password-authenticated key exchange
+opaque-ke           = { workspace = true }
+argon2              = { workspace = true }
+
+# Crypto — MLS (M2)
+openmls             = { workspace = true }
+openmls_rust_crypto = { workspace = true }
+openmls_traits      = { workspace = true }
+tls_codec           = { workspace = true }
+serde               = { workspace = true }
+bincode             = { workspace = true }
+serde_json          = { workspace = true }
+
+# Serialisation
+capnp               = { workspace = true }
+quicproquo-proto       = { path = "../quicproquo-proto" }
+
+# Async runtime
+tokio               = { workspace = true }
+
+# Error handling
+thiserror           = { workspace = true }
+
+[dev-dependencies]
+tokio               = { workspace = true }
+criterion           = { version = "0.5", features = ["html_reports"] }
+prost               = "0.13"
+
+[[bench]]
+name = "serialization"
+harness = false
+
+[[bench]]
+name = "mls_operations"
+harness = false
+
+[[bench]]
+name = "hybrid_kem_bench"
+harness = false