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>

crates/quicproquo-server/migrations/004_federation.sql

@@ -0,0 +1,16 @@
+-- 004_federation.sql: Federation support tables.
+
+-- Map identity keys to their home server domain.
+-- Used for routing: if a recipient's home_server != local domain, relay via federation.
+CREATE TABLE IF NOT EXISTS identity_home_servers (
+    identity_key BLOB PRIMARY KEY,
+    home_server  TEXT NOT NULL,
+    updated_at   INTEGER NOT NULL
+);
+
+-- Known federation peers (other quicnprotochat servers).
+CREATE TABLE IF NOT EXISTS federation_peers (
+    domain    TEXT PRIMARY KEY,
+    last_seen INTEGER NOT NULL,
+    is_active INTEGER NOT NULL DEFAULT 1
+);