chore(branding): rebrand FixMate to CityPulse across codebase

- Update product name in README, backend docs, and design tokens
- Rename Flutter root widget to CityPulseApp and update tests
- Update dashboard brand strings and HTML title
- Refresh i18n strings (en/ms) and welcome taglines
- Adjust backend API title/description and root message
- Minor formatting in ApiService comments; no logic changes
- Update Android/iOS manifest comments and pubspec description

No API endpoints or response schema changes.

assets/tokens/design-tokens.json

@@ -1,6 +1,6 @@
 {
   "meta": {
-    "name": "FixMate Design Tokens",
+    "name": "CityPulse Design Tokens",
     "version": "1.0.0",
     "brand": "Civic Premium – Citizen First"
   },