feat: add overtime tracking support with configurable working hours

Implement comprehensive overtime tracking feature that allows users to
set their standard working hours per day and automatically calculates
overtime for hours worked beyond that threshold.

Core Features:
- Add standard_hours_per_day field to User model (default: 8.0 hours)
- Create Alembic migration (031_add_standard_hours_per_day.py)
- Implement overtime calculation utilities (app/utils/overtime.py)
  * calculate_daily_overtime: per-day overtime calculation
  * calculate_period_overtime: multi-day overtime aggregation
  * get_daily_breakdown: detailed day-by-day analysis
  * get_weekly_overtime_summary: weekly overtime statistics
  * get_overtime_statistics: comprehensive overtime metrics

User Interface:
- Add "Overtime Settings" section to user settings page
- Display overtime data in user reports (regular vs overtime hours)
- Show "Days with Overtime" badge in reports
- Add overtime analytics API endpoint (/api/analytics/overtime)
- Improve input field styling with cleaner appearance (no spinners)

Reports Enhancement:
- Standardize form input styling across all report pages
- Replace inline Tailwind classes with consistent form-input class
- Add FontAwesome icons to form labels for better UX
- Improve button hover states and transitions

Testing:
- Add comprehensive unit tests (tests/test_overtime.py)
- Add smoke tests for quick validation (tests/test_overtime_smoke.py)
- Test coverage for models, utilities, and various overtime scenarios

Documentation:
- OVERTIME_FEATURE_DOCUMENTATION.md: complete feature guide
- OVERTIME_IMPLEMENTATION_SUMMARY.md: technical implementation details
- docs/features/OVERTIME_TRACKING.md: quick start guide

This change enables organizations to track employee overtime accurately
based on individual working hour configurations, providing better
insights into work patterns and resource allocation.

docs/features/OVERTIME_TRACKING.md

@@ -0,0 +1,133 @@
+# Overtime Tracking Feature
+
+## Quick Start
+
+The Overtime Tracking feature allows users to track hours worked beyond their standard workday.
+
+### For Users
+
+1. **Set Your Standard Hours**
+   - Go to Settings → Overtime Settings
+   - Enter your standard working hours per day (e.g., 8.0)
+   - Click Save
+
+2. **View Your Overtime**
+   - Navigate to Reports → User Report
+   - Select your date range
+   - View overtime breakdown in the report table
+
+### For Developers
+
+**Key Files:**
+- `app/utils/overtime.py` - Core calculation functions
+- `app/models/user.py` - User model with standard_hours_per_day field
+- `app/routes/reports.py` - Report route with overtime display
+- `app/routes/analytics.py` - Analytics API endpoint
+- `migrations/versions/031_add_standard_hours_per_day.py` - Database migration
+
+**API Endpoint:**
+```
+GET /api/analytics/overtime?days=30
+```
+
+**Key Functions:**
+```python
+from app.utils.overtime import (
+    calculate_daily_overtime,
+    calculate_period_overtime,
+    get_daily_breakdown,
+    get_overtime_statistics
+)
+```
+
+### Testing
+
+```bash
+# Run all overtime tests
+pytest tests/test_overtime.py tests/test_overtime_smoke.py -v
+
+# With coverage
+pytest tests/test_overtime*.py --cov=app.utils.overtime --cov-report=html
+```
+
+### Documentation
+
+- **Full Documentation**: [OVERTIME_FEATURE_DOCUMENTATION.md](../../OVERTIME_FEATURE_DOCUMENTATION.md)
+- **Implementation Summary**: [OVERTIME_IMPLEMENTATION_SUMMARY.md](../../OVERTIME_IMPLEMENTATION_SUMMARY.md)
+
+## How It Works
+
+1. User sets standard hours per day in settings (default: 8.0)
+2. System tracks all time entries as usual
+3. When viewing reports, system calculates:
+   - For each day: regular hours (up to standard) + overtime hours (beyond standard)
+4. Reports display:
+   - Total hours worked
+   - Regular hours (green)
+   - Overtime hours (orange)
+   - Days with overtime
+
+## Examples
+
+### Example 1: Full-time Employee (8 hours/day)
+- Monday: 8 hours → 8 regular, 0 overtime
+- Tuesday: 10 hours → 8 regular, 2 overtime
+- Wednesday: 7 hours → 7 regular, 0 overtime
+
+### Example 2: Part-time Employee (6 hours/day)
+- Monday: 6 hours → 6 regular, 0 overtime
+- Tuesday: 7 hours → 6 regular, 1 overtime
+- Wednesday: 5 hours → 5 regular, 0 overtime
+
+## Configuration
+
+**User Setting:** `standard_hours_per_day`
+- Type: Float
+- Default: 8.0
+- Range: 0.5 to 24.0
+- Location: User Settings → Overtime Settings
+
+## Database
+
+**Table:** `users`
+**Column:** `standard_hours_per_day`
+- Type: `FLOAT`
+- Default: `8.0`
+- Nullable: `NO`
+
+**Migration:** `031_add_standard_hours_per_day`
+
+## Features
+
+✅ User-configurable standard hours  
+✅ Automatic overtime calculation  
+✅ Display in user reports  
+✅ Analytics API endpoint  
+✅ Daily overtime breakdown  
+✅ Weekly overtime summaries  
+✅ Comprehensive statistics  
+✅ Full test coverage  
+✅ Complete documentation  
+
+## Future Enhancements
+
+- Weekly overtime thresholds
+- Overtime approval workflows
+- Overtime pay rate calculations
+- Email notifications for excessive overtime
+- Overtime budget limits
+- Export overtime reports
+
+## Support
+
+For questions or issues:
+1. Review the [full documentation](../../OVERTIME_FEATURE_DOCUMENTATION.md)
+2. Check test cases for examples
+3. Open a GitHub issue
+
+---
+
+**Version:** 1.0.0  
+**Status:** ✅ Production Ready  
+**Last Updated:** October 27, 2025
+