fix(window,login): grant set-title capability + shrink login logo 20%

- Add core:window:allow-set-title to capabilities/default.json. Tauri 2
  rejects setTitle() from the frontend unless the capability is
  explicitly granted; without this the window-title feature silently
  fell back to "QBZ" in every case.
- Login logo: 175px -> 140px (-20%) per feedback.
- Drop the debug console logging on the title effect now that the
  wiring is confirmed working; keep the warn-on-failure.

cc

src-tauri/capabilities/default.json

@@ -28,6 +28,7 @@
     "core:window:allow-inner-size",
     "core:window:allow-inner-position",
     "core:window:allow-set-position",
+    "core:window:allow-set-title",
     "core:webview:default",
     "core:webview:allow-create-webview-window",
     "core:webview:allow-webview-close",