feat: Add bulk time entry feature for quick multi-day time logging

[evilguy4000]

• Add comprehensive bulk time entry system allowing users to create multiple time entries across date ranges
• Implement smart date range selection with weekend skipping option (max 31 days)
• Add real-time preview showing affected dates, total days, and hours before creation
• Include robust validation: conflict detection, overlap prevention, and data integrity checks
• Create responsive UI with mobile optimization and accessibility features
• Integrate with existing project/task system maintaining full compatibility
• Add navigation links in main menu and dashboard quick actions
• Implement atomic database transactions for reliable bulk operations
• Support consistent time patterns (same start/end time across all days)
• Include comprehensive documentation and user guidance

Routes added:

• GET/POST /timer/bulk - Main bulk entry form
• GET /timer/bulk/<project_id> - Project-specific bulk entry

UI improvements:

• New bulk entry form with live preview and validation
• Updated navigation dropdown with bulk entry option
• Added bulk entry card to dashboard quick actions
• Mobile-responsive design with touch-friendly interface

This feature significantly reduces time entry overhead for users with regular work patterns, enabling creation of a full work week in seconds instead of minutes per day.

[github-actions]

CI Pipeline Status

All checks passed! ✅

Completed Checks:

• ✅ Database migration tests (PostgreSQL & SQLite)
• ✅ Docker build and startup test
• ✅ Security vulnerability scan

Ready for review and merge 🚀

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