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.

proto/qpc/v1/device.proto

@@ -0,0 +1,55 @@
+syntax = "proto3";
+package qpc.v1;
+
+// Device register/list/revoke (3 methods).
+// Method IDs: 700-702.
+
+message RegisterDeviceRequest {
+  bytes device_id = 1;
+  string device_name = 2;
+}
+
+message RegisterDeviceResponse {
+  bool success = 1;
+}
+
+message ListDevicesRequest {}
+
+message ListDevicesResponse {
+  repeated Device devices = 1;
+}
+
+message Device {
+  bytes device_id = 1;
+  string device_name = 2;
+  uint64 registered_at = 3;
+}
+
+message RevokeDeviceRequest {
+  bytes device_id = 1;
+}
+
+message RevokeDeviceResponse {
+  bool success = 1;
+}
+
+// Push notification token registration.
+// Method ID: 710.
+// Clients call this after login to register their device for push notifications.
+
+enum PushPlatform {
+  PUSH_PLATFORM_UNSPECIFIED = 0;
+  PUSH_PLATFORM_APNS = 1;        // Apple Push Notification Service (iOS)
+  PUSH_PLATFORM_FCM = 2;         // Firebase Cloud Messaging (Android)
+  PUSH_PLATFORM_WEB_PUSH = 3;    // Web Push (browsers)
+}
+
+message RegisterPushTokenRequest {
+  bytes device_id = 1;
+  PushPlatform platform = 2;
+  string token = 3;              // Platform-specific push token
+}
+
+message RegisterPushTokenResponse {
+  bool success = 1;
+}