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>

docs/src/internals/storage-backend.md

@@ -1,14 +1,14 @@
 # Storage Backend
 
-quicnprotochat uses two storage backends: `FileBackedStore` on the server side
+quicproquo uses two storage backends: `FileBackedStore` on the server side
 for KeyPackages and delivery queues, and `DiskKeyStore` on the client side for
 MLS cryptographic key material. Both follow the same pattern: in-memory data
 structures backed by optional file persistence, with full serialization on every
 write.
 
 **Sources:**
-- `crates/quicnprotochat-server/src/storage.rs` (FileBackedStore)
-- `crates/quicnprotochat-core/src/keystore.rs` (DiskKeyStore, StoreCrypto)
+- `crates/quicproquo-server/src/storage.rs` (FileBackedStore)
+- `crates/quicproquo-core/src/keystore.rs` (DiskKeyStore, StoreCrypto)
 
 ---
 
@@ -52,7 +52,7 @@ File paths:
 - `{dir}/hybridkeys.bin` -- Hybrid public keys
 
 The default data directory is `data/`, configurable via `--data-dir` /
-`QUICNPROTOCHAT_DATA_DIR`.
+`QPQ_DATA_DIR`.
 
 ### Flush-on-Every-Write
 
@@ -233,7 +233,7 @@ fn keystore_path(state_path: &Path) -> PathBuf {
 }
 ```
 
-So `quicnprotochat-state.bin` produces a key store at `quicnprotochat-state.ks`.
+So `qpq-state.bin` produces a key store at `quicproquo-state.ks`.
 
 ### Persistence Format