[MOBILE] Replace emoji tab-icon stubs with real icons

[Cedarich]

Complexity: Trivial (100)

Description
app/(tabs)/_layout.tsx contains a TabIcon component that renders text glyphs (≡, bell emoji, full-width plus) with a comment saying it will be "replaced by @expo/vector-icons at runtime" — which never happens. lucide-react-native is already a dependency and is the icon library used elsewhere in the app.

Acceptance Criteria

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

[Olayiwola2904]

@Olayiwola2904 has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

Hi Maintainer! I’m interested in working on this task and can deliver a clean solution on time.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @Olayiwola2904 to this issue.

[David-282]

@David-282 has applied to work on this issue as part of the Stellar Wave Program's 8th wave.

kindly assign to me

ℹ️ Repo Maintainers: To accept this application, review their application or assign @David-282 to this issue.

[drips-wave]

Congratulations, @Olayiwola2904! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on August 31, 2026.

🧑‍💻 @Olayiwola2904: Please resolve the issue such that the repo's maintainers have enough time to review your contribution before the due date. You'll earn Points for completing the issue on-time, which will make you eligible for a share of the Stellar Wave Program's reward pool.

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