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/008_devices.sql

@@ -0,0 +1,8 @@
+CREATE TABLE IF NOT EXISTS devices (
+    identity_key BLOB NOT NULL,
+    device_id BLOB NOT NULL,
+    device_name TEXT NOT NULL DEFAULT '',
+    registered_at INTEGER NOT NULL DEFAULT (strftime('%s','now')),
+    PRIMARY KEY (identity_key, device_id)
+);
+CREATE INDEX IF NOT EXISTS idx_devices_identity ON devices(identity_key);