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/cryptography/identity-keys.md

@@ -1,11 +1,11 @@
 # Ed25519 Identity Keys
 
 The Ed25519 identity keypair is the long-term cryptographic identity of a
-quicnprotochat client. It is generated once, persisted across sessions, and used
+quicproquo client. It is generated once, persisted across sessions, and used
 for MLS credential signing, Authentication Service registration, and delivery
 queue addressing.
 
-**Source:** `crates/quicnprotochat-core/src/identity.rs`
+**Source:** `crates/quicproquo-core/src/identity.rs`
 
 ## Structure
 
@@ -37,7 +37,7 @@ A fresh identity keypair is generated from the OS CSPRNG (`OsRng`) via
 `ed25519-dalek`:
 
 ```rust
-use quicnprotochat_core::identity::IdentityKeypair;
+use quicproquo_core::identity::IdentityKeypair;
 
 let identity = IdentityKeypair::generate();
 // The signing key seed is generated from OsRng (getrandom on Linux).