feat(ui): revamp onboarding, map, capture/review, and theme

- Redesign WelcomeScreen and OnboardingFlow with gradients, branding,
  and updated messaging; refresh bottom navigation styling and
  animations
- Enhance MapScreen with severity-based marker styling, category
  icons, improved cluster bubbles, legend overlay, and polished
  filter modal; refine camera fit and device centering logic
- Revamp CaptureScreen and ReviewScreen UX with modern cards,
  AI analysis section, improved selection controls, and clearer
  notes/location presentation
- Update theme to civic palette with expanded neutrals, surface
  containers, and refined button styles
- Expand design tokens: add civic colors, light variants, and
  gradient definitions; align semantic mappings
- Refresh English copy in en.json for welcome and onboarding
- Redesign ReportCard with icons, severity/status chips, improved
  layout, and action menus

Note: some new UI strings are temporarily hardcoded (English) and
will be moved to i18n assets in a follow-up.

assets/lang/en.json

@@ -81,19 +81,19 @@
   "lang.en": "English",
   "lang.ms": "Bahasa Malaysia",
   "welcome.title": "Spot it. Snap it. Fix it.",
-  "welcome.subtitle": "Report city issues in seconds—help crews act faster.",
+  "welcome.subtitle": "Report city issues in seconds with AI-powered detection. Help create safer, better communities together.",
   "cta.continueGuest": "Continue as guest",
   "cta.signIn": "Sign in",
   "cta.skip": "Skip",
   "cta.next": "Next",
   "cta.getStarted": "Get started",
   "onboarding.header": "Welcome to FixMate",
-  "onboarding.title1": "Fast capture",
-  "onboarding.body1": "Take a photo and submit in under a minute.",
-  "onboarding.title2": "Map clarity",
-  "onboarding.body2": "See issues around you with smart clustering.",
-  "onboarding.title3": "Track progress",
-  "onboarding.body3": "Follow status updates as work gets done.",
+  "onboarding.title1": "Fast Issue Reporting",
+  "onboarding.body1": "Simply take a photo of any urban issue - our AI automatically identifies and categorizes the problem in seconds.",
+  "onboarding.title2": "Smart City Mapping",
+  "onboarding.body2": "View all reported issues on an interactive map with intelligent clustering and filtering options.",
+  "onboarding.title3": "Track Progress",
+  "onboarding.body3": "Follow the status of your reports from submission to resolution. Help make your community better.",
   "auth.title": "Sign in",
   "auth.signInWithApple": "Sign in with Apple",
   "auth.signInWithGoogle": "Sign in with Google",