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/roadmap/phase2-and-m4-m6.md

@@ -21,7 +21,7 @@ The following legacy behaviour has been removed; only current behaviour is suppo
 
 | Task | Status | Notes |
 |------|--------|-------|
-| **Ciphersuite allowlist** | **Done** | Server rejects KeyPackages whose ciphersuite is not `MLS_128_DHKEMX25519_AES128GCM_SHA256_Ed25519`. See `quicnprotochat_core::validate_keypackage_ciphersuite` and `upload_key_package` (E021). |
+| **Ciphersuite allowlist** | **Done** | Server rejects KeyPackages whose ciphersuite is not `MLS_128_DHKEMX25519_AES128GCM_SHA256_Ed25519`. See `quicproquo_core::validate_keypackage_ciphersuite` and `upload_key_package` (E021). |
 | **ALPN enforcement** | **Done** | Server TLS config sets `alpn_protocols = [b"capnp"]`; handshake completes only if client offers `capnp`. |
 | **Connection draining** | **Done** | On `Ctrl+C`, server calls `endpoint.close(0, b"server shutdown")` and exits the accept loop. |
 | **Wire versioning** | **Done** | `enqueue`, `fetch`, `fetchWait` require `version == CURRENT_WIRE_VERSION` (1). Other RPCs use auth version. |