refactor: unify user profile endpoints with query parameters

Removed Endpoints

• ❌ GET /users/{user_id}/streaks
• ❌ GET /users/{user_id}/activity-timeline
• ❌ GET /users/{user_id}/profile-summary

Added Endpoint

• ✅ GET /users/{user_id}/profile - Unified profile endpoint with optional query parameters

New Endpoint Features

Base Response:

• Always returns user_id and user_name

Optional Includes (via ?include= query parameter):

• streaks - Adds streak data (contributions, edits, combined streaks)
• timeline - Adds 30-day activity timeline
• summary - Adds comprehensive profile summary with contribution stats

Usage Examples:

• GET /users/{user_id}/profile - Basic user info
• GET /users/{user_id}/profile?include=streaks - User info + streak data
• GET /users/{user_id}/profile?include=streaks,timeline - User info + streaks + timeline
• GET /users/{user_id}/profile?include=streaks,timeline,summary - All data

Benefits

• Simplified API - One endpoint instead of four
• Flexible data fetching - Client controls what data to include
• Better performance - Only fetch needed data
• Public access - No authentication required (all endpoints are public)

Files Modified

• app/api/v1/endpoints/users.py - Removed 3 endpoints, added 1 unified endpoint
• app/schemas/record_history.py - Added date import