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/forward-secrecy.md

@@ -6,7 +6,7 @@ compromised, past session keys cannot be recovered.** In other words, an
 attacker who obtains today's long-term key cannot use it to decrypt messages
 recorded yesterday.
 
-quicnprotochat provides forward secrecy at two independent layers: the transport
+quicproquo provides forward secrecy at two independent layers: the transport
 layer and the application layer. Even if one layer's FS mechanism is defeated,
 the other continues to protect message confidentiality.
 
@@ -28,7 +28,7 @@ In each TLS 1.3 handshake:
 
 Because the ephemeral keys exist only for the duration of the handshake,
 compromising the server's long-term TLS certificate key (currently self-signed
-in quicnprotochat) does not reveal past session keys.
+in quicproquo) does not reveal past session keys.
 
 ## Application Layer Forward Secrecy
 
@@ -54,7 +54,7 @@ This deletion is the mechanism that provides forward secrecy: once old epoch
 keys are erased, messages encrypted under those keys cannot be decrypted, even
 if the current group state is compromised.
 
-In quicnprotochat, epoch advancement occurs when:
+In quicproquo, epoch advancement occurs when:
 
 - `add_member()` is called, which creates a Commit and calls
   `merge_pending_commit()`.
@@ -91,7 +91,7 @@ HPKE init keys.
 
 ## Layered Forward Secrecy
 
-A distinctive property of quicnprotochat's design is that forward secrecy
+A distinctive property of quicproquo's design is that forward secrecy
 operates at two independent layers:
 
 ```text
@@ -135,7 +135,7 @@ unless they also break the transport encryption.
 Signal's Double Ratchet protocol also provides forward secrecy, but the
 mechanisms differ:
 
-| Property | Signal Double Ratchet | MLS (quicnprotochat) |
+| Property | Signal Double Ratchet | MLS (quicproquo) |
 |----------|----------------------|---------------------|
 | Scope | Pairwise (1:1 sessions) | Group (n-party) |
 | Ratchet granularity | Per message (symmetric ratchet) + per DH round (DH ratchet) | Per epoch (Commit) |