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/production-readiness.md

@@ -1,6 +1,6 @@
 # Production Readiness WBS
 
-This page defines the work breakdown structure (WBS) for taking quicnprotochat
+This page defines the work breakdown structure (WBS) for taking quicproquo
 from a proof-of-concept to a production-hardened system. It covers feature scope,
 security policy, phased delivery, and a planning checklist.
 
@@ -11,7 +11,7 @@ document focuses on the cross-cutting concerns that span multiple milestones.
 
 ## Feature Scope (Must-Have)
 
-These are the feature areas that must be addressed before quicnprotochat can be
+These are the feature areas that must be addressed before quicproquo can be
 considered production-ready. Each area maps to one or more milestones or phases
 in the WBS below.
 
@@ -30,7 +30,7 @@ in the WBS below.
 
 ## Security Plan (By Design)
 
-quicnprotochat follows a security-by-design philosophy. The standards below are
+quicproquo follows a security-by-design philosophy. The standards below are
 non-negotiable -- see [Coding Standards](../contributing/coding-standards.md) for
 how they are enforced in code.