[Viviiii16]

This pull request introduces the "Share Trip" and "SOS" emergency safety features for riders during active trips.

1. Frontend Components & UI

Created SafetyActionsBar.tsx (mobile/src/components/SafetyActionsBar.tsx):**
Built a responsive, dark-themed safety action bar containing the "Share Trip" and "SOS" buttons.
Integrated Share Trip functionality: calls the backend sharing endpoint and utilizes native OS sharing (react-native Share API) on mobile or writes the tracking URL directly to the clipboard on web platforms.

Integrated SOS functionality: triggers a confirmation modal warning the user, non-blockingly launches the emergency dialer (tel:112), and concurrently logs the user's live GPS coordinates (lat, lng) to the server.

Rider Screen Integration (mobile/app/(rider)/ride/[id].tsx):
Integrated the SafetyActionsBar into the active rider interface sheet.
Configured conditional rendering to display the safety controls dynamically across active ride states (driver_assigned, driver_arrived, and in_progress).

2. API Client & Networking

Expanded API Interface (mobile/src/lib/api.ts):
Added shareTrip(rideId) to fetch secure tracking URLs from the FastAPI backend.
Added triggerSOS(rideId, lat, lng) to transmit real-time emergency coordinates and record safety logs.

3. Backend Services & Migrations

Backend Database & Schemas (backend/):
Added Alembic migrations to support ride sharing and emergency SOS event logging in the database schema.
Implemented corresponding FastAPI endpoints (/rides/{id}/share and /rides/{id}/sos) to handle token generation and emergency telemetry.

4. Testing & Verification:-
   Passed all TypeScript type checks (npx tsc --noEmit), linter evaluations (npx eslint), and Python test suites (python test_all.py --quick).

Closes #19