release: bump version to 1.4(p) (versionCode 14)

- Update versionCode 12 → 14, versionName 1.3(p) → 1.4(p)
- Update pubspec.yaml version to 1.4.0+14
- Add CHANGELOG.md with full version history
- Update README.md: version badge + changelog section
- Desktop Contribute Dashboard rebuilt to match web version
  - Contributor Dashboard title, 3-tab nav (Contribute/Leaderboard/Achievements)
  - Two-column submit form, tier milestone progress bar
  - Desktop leaderboard with podium, filters, rank table (green points)
  - Desktop achievements 3-column badge grid
  - Inline Reward Shop with RP balance
- Gamification feature module (EP, RP, leaderboard, achievements, shop)
- Profile screen redesigned to match web app layout with animations
- Home screen bottom sheet date filter chips
- Updated API endpoints, login/event detail screens, theme colors
- Added Gilroy font suite, responsive layout improvements

.gitignore

@@ -46,3 +46,7 @@ app.*.map.json
 /android/app/profile
 /android/app/release
 web/assets/login-bg.mp4
+
+# Keystore files (signing keys)
+*.jks
+*.keystore