feat(ui): GUI debug logging follows daemon log level + debug bundle

When the daemon is set to debug/trace, the GUI now automatically writes a
rotated gui-client.log in the user's config dir and the daemon's debug bundle
collects it. The UI learns the level both at startup (daemon already in debug)
and live, by piggybacking the existing SubscribeEvents stream: the daemon
publishes a marked log-level-changed SystemEvent (and a per-subscription
snapshot), which DaemonFeed routes to guilog.DebugLog instead of an OS toast.
The UI registers its log path via a new RegisterUILog RPC so the root daemon,
which can't resolve the user's config dir, knows where to find the file.

Manual --log-file (any value) disables the daemon-driven file logging.

Fix: client/ui SetLogLevel looked up proto.LogLevel_value with the lowercase
logrus name, which never matched the uppercase enum keys and silently fell back
to INFO — so trace/debug requests from the bundle flow had no effect.

client/proto/daemon.proto

@@ -85,6 +85,11 @@ service DaemonService {
 
   rpc GetEvents(GetEventsRequest) returns (GetEventsResponse) {}
 
+  // RegisterUILog records the desktop UI's absolute log path so the daemon's
+  // debug bundle can collect it (the daemon runs as root and can't resolve the
+  // user's config dir).
+  rpc RegisterUILog(RegisterUILogRequest) returns (RegisterUILogResponse) {}
+
   rpc SwitchProfile(SwitchProfileRequest) returns (SwitchProfileResponse) {}
 
   rpc SetConfig(SetConfigRequest) returns (SetConfigResponse) {}
@@ -547,6 +552,13 @@ message SetLogLevelRequest {
 message SetLogLevelResponse {
 }
 
+message RegisterUILogRequest {
+  string path = 1;
+}
+
+message RegisterUILogResponse {
+}
+
 // State represents a daemon state entry
 message State {
   string name = 1;