chore: rename quicproquo → quicprochat in Rust workspace

Rename all crate directories, package names, binary names, proto
package/module paths, ALPN strings, env var prefixes, config filenames,
mDNS service names, and plugin ABI symbols from quicproquo/qpq to
quicprochat/qpc.

crates/quicprochat-server/migrations/001_initial.sql

@@ -0,0 +1,47 @@
+CREATE TABLE IF NOT EXISTS key_packages (
+    id           INTEGER PRIMARY KEY AUTOINCREMENT,
+    identity_key BLOB NOT NULL,
+    package_data BLOB NOT NULL,
+    created_at   INTEGER DEFAULT (strftime('%s','now'))
+);
+
+CREATE TABLE IF NOT EXISTS deliveries (
+    id            INTEGER PRIMARY KEY AUTOINCREMENT,
+    recipient_key BLOB NOT NULL,
+    channel_id    BLOB NOT NULL DEFAULT X'',
+    payload       BLOB NOT NULL,
+    created_at    INTEGER DEFAULT (strftime('%s','now'))
+);
+
+CREATE TABLE IF NOT EXISTS hybrid_keys (
+    identity_key      BLOB PRIMARY KEY,
+    hybrid_public_key BLOB NOT NULL
+);
+
+CREATE INDEX IF NOT EXISTS idx_kp_identity
+    ON key_packages(identity_key);
+
+CREATE INDEX IF NOT EXISTS idx_del_recipient_channel
+    ON deliveries(recipient_key, channel_id);
+
+CREATE TABLE IF NOT EXISTS server_setup (
+    id         INTEGER PRIMARY KEY CHECK (id = 1),
+    setup_data BLOB NOT NULL
+);
+
+CREATE TABLE IF NOT EXISTS users (
+    username      TEXT PRIMARY KEY,
+    opaque_record BLOB NOT NULL,
+    created_at    INTEGER DEFAULT (strftime('%s','now'))
+);
+
+CREATE TABLE IF NOT EXISTS user_identity_keys (
+    username     TEXT PRIMARY KEY,
+    identity_key BLOB NOT NULL
+);
+
+CREATE TABLE IF NOT EXISTS endpoints (
+    identity_key BLOB PRIMARY KEY,
+    node_addr    BLOB NOT NULL,
+    updated_at   INTEGER DEFAULT (strftime('%s','now'))
+);