fix(mobile): replace emoji tab-icon stubs with real icons

[Olayiwola2904]

Overview

This PR replaces the temporary emoji/text glyph stubs in the mobile tab bar with proper lucide-react-native icons. The previous TabIcon component rendered text glyphs (≡, bell emoji, full-width plus) and left a comment saying it would be "replaced by @expo/vector-icons at runtime" — which never happened. This change wires tabBarIcon directly to lucide-react-native components, forwarding color and size props so active/inactive tint colors are preserved and no emoji font fallback occurs on iOS or Android.

Related Issue

Closes #

Changes

🖼️ Tab Icon Replacement

• [REPLACE] apps/frontend/app/(tabs)/_layout.tsx
  • Removed the TabIcon component that rendered text glyphs with a runtime-replacement comment.
  • Replaced the glyph stubs with lucide-react-native icons (Menu, Bell, Plus) in the tabBarIcon render prop.
  • Updated the render prop to pass color and size directly to the icon components.
  • Eliminated the emoji font fallback and the unused @expo/vector-icons comment.

Verification Results

npm run lint -- "apps/frontend/app/(tabs)/_layout.tsx"
✅ Lint passed

Manual acceptance check:
✅ Tab icons render with lucide-react-native icons (no emoji fallback)
✅ Active/inactive tint colours apply correctly
✅ Icons respect color and size props from tabBarIcon

Acceptance Criteria	Status
TabIcon glyph stub is removed and replaced with lucide-react-native icons	✅ Done
Icons respect the color and size props supplied by tabBarIcon	✅ Verified
Active and inactive tint colours still apply correctly	✅ Verified
Icons render consistently on iOS and Android with no emoji font fallback	✅ Verified

Closes #554

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[KuchiMercy]

Kindly review