fix(patient): Remove unused and duplicate imports across patient app

## Summary

Running `flutter analyze` on the `patient/` app reveals **10 unused import warnings** and **2 duplicate import warnings** across 8 files. These are `warning`-level diagnostics that clutter the codebase and can mask real dependency issues.

## Affected Files

| File | Issue |
|------|-------|
| `lib/core/repository/auth/auth_repository.dart` | `unused_import`: `package:flutter/material.dart` |
| `lib/presentation/assessments/assessment_screen.dart` | `unused_import`: `package:patient/presentation/result/result.dart` |
| `lib/presentation/auth/consultation_request_screen.dart` | `unused_import`: `package:patient/core/repository/auth/auth.dart`, `slot_booking_card.dart` |
| `lib/presentation/auth/consultation_slot_booking_screen.dart` | `unused_import`: `auth_provider.dart`, `provider.dart` |
| `lib/presentation/auth/personal_details_screen.dart` | `unused_import`: `assessment_screen.dart`, `home_screen.dart`; `duplicate_import` |
| `lib/presentation/result/result.dart` | `unused_import`: `dart:convert`, `flutter_dotenv`, `http` |
| `lib/provider/reports_provider.dart` | `unused_import`: `../gen/assets.gen.dart` |
| `lib/provider/therapist_provider.dart` | `unused_import`: `flutter_dotenv`, `assessment_card_model.dart`, `supabase_assessments_repository.dart`; `duplicate_import` |

## Steps to Reproduce

```
cd patient
flutter analyze
```

## Expected Behavior

`flutter analyze` reports no `unused_import` or `duplicate_import` warnings.

## Fix

Remove each flagged import. Where a `duplicate_import` exists, remove the duplicate line.