DOC: Update TRANSLATIONS.md to reflect current auto-generation workflow

The TRANSLATIONS.md guide contains outdated instructions that don't match the current implementation. It tells contributors to manually edit `supportedLocales` in 'main.dart', but this is now auto-generated by `flutter gen-l10n`

Issues:
1. Outdated workflow: Instructs manual editing of `supportedLocales` array in `main.dart`
2. Wrong file reference: Points to `main.dart` instead of auto-generated files
3. Incomplete language list: Shows only 2 languages, but we support 7 (bn, en, gu, hi, kn, mr, pa)

Proposed Fix:
- Remove "Update main.dart" step
- Add `flutter gen-l10n` generation step
- Update supported languages list
- Update commit message examples (reference PR #610 )

@M4dhav Can this issue be assigned to me? I have a the update ready to submit