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>

.github/CODEOWNERS

@@ -1,4 +1,4 @@
-# Code owners for quicnprotochat. PRs require review from owners.
+# Code owners for quicproquo. PRs require review from owners.
 # See https://docs.github.com/en/repositories/managing-your-repositorys-settings-and-features/customizing-your-repository/about-code-owners
 # Replace 'maintainers' with your GitHub user/team handle.
 
@@ -6,10 +6,10 @@
 * @maintainers
 
 # Crate-specific (uncomment and add handles when you have designated owners)
-# /crates/quicnprotochat-core/     @owner1
-# /crates/quicnprotochat-proto/    @owner1
-# /crates/quicnprotochat-server/   @owner1
-# /crates/quicnprotochat-client/   @owner1
-# /crates/quicnprotochat-p2p/      @owner1
+# /crates/quicproquo-core/     @owner1
+# /crates/quicproquo-proto/    @owner1
+# /crates/quicproquo-server/   @owner1
+# /crates/quicproquo-client/   @owner1
+# /crates/quicproquo-p2p/      @owner1
 # /schemas/                        @owner1
 # /docs/                           @owner1