fix: Remove unused declarations (unused_element, unused_field, unused_local_variable)

## Summary

`flutter analyze` reports several **unused declaration** warnings across both apps. Unused code is dead weight — it confuses readers and can indicate logic that was never wired up correctly.

## Affected Declarations

### patient app
| File | Symbol | Kind |
|------|--------|------|
| `lib/presentation/activities/daily_activities_screen.dart:41` | `_animateProgress` | `unused_element` (private method) |
| `lib/provider/appointments_provider.dart:151` | `_formatTimeOfDay` | `unused_element` (private method) |
| `lib/provider/task_provider.dart:9` | `_apiStatus` | `unused_field` (private field) |

### therapist app
| File | Symbol | Kind |
|------|--------|------|
| `lib/presentation/auth/auth_screen.dart:48` | `isNewUser` | `unused_local_variable` |
| `lib/presentation/consultation/consultation_request_detail_screen.dart:375` | `_buildNotesSection` | `unused_element` (private method) |
| `lib/presentation/consultation/consultation_request_detail_screen.dart:483` | `_buildDetailRow` | `unused_element` (private method) |
| `lib/presentation/home/home_screen.dart:286` | `_buildConsultationRequestSection` | `unused_element` (private method) |
| `lib/presentation/therapy_goals/add_therapy_details_screen.dart:235` | `key` parameter | `unused_element_parameter` |

## Steps to Reproduce

```
cd patient && flutter analyze
cd ../therapist && flutter analyze
```

## Fix

- Remove unused private methods, fields, and local variables.
- For the unused `key` parameter: remove the optional parameter or use it correctly.