feat: tray-first UX, text outline, start-at-login toggle, font max 200

- All settings move to flat tray menu; right-click on clock disabled
- ClockLabel: custom QPainterPath text rendering with configurable
  glyph outline (BorderColor) — verified pixel-level offscreen
- Fixed glyph positioning bug (baseline math) caught by isolated test
- Window auto-fits content (adjustSize) — no more oversized clock
- Start at Login: checkable tray item, persisted in QSettings,
  LaunchAgent enable/disable (TDD: roundTrip test caught disable()
  returning false when plist already absent)
- Color dialog: hex/HTML input + 'transparent' + native picker fallback;
  opaque colors stored as #RRGGBB
- Border: glyph outline instead of box border; background still painted
  in paintEvent (QSS doesn't render with WA_TranslucentBackground on macOS)
- Removed window shadow (setHasShadow:NO), no bold, SF Pro Rounded
- Font size dialogs allow up to 200 (was 72)
- macOS: icon template 16pt, light/dark auto-adapt; LaunchAgent points
  to /Applications install

autostart_manager.h

@@ -7,9 +7,10 @@ class AutoStartManager
 {
 public:
     static bool enableForCurrentApplication();
+    static bool enableForPath(const QString &executablePath);
+    static bool disable();
+    static bool isEnabled();
     static QString launchAgentContents(const QString &executablePath);
-
-private:
     static QString launchAgentPath();
 };