Add completion rate grading feature to Key Results (0%-100%)

[Copilot]

This PR implements a comprehensive grading system for Key Results, allowing users to track completion progress from 0% to 100%.

What's Changed

Core Functionality

• New CompletionRate Property: Added decimal field to KeyResult model storing values from 0.0 to 1.0 (representing 0%-100%)
• Database Migration: Created migration to add CompletionRate column with proper decimal precision
• Validation: Range validation ensures completion rates stay within valid bounds (0.0-1.0)
• Controller Updates: Enhanced KeyResult controller to handle completion rate in Create, Read, Update operations

User Interface Enhancements

• User-Friendly Input: Forms now accept percentage values (0-100%) with automatic conversion to decimal storage
• Visual Progress Indicators: Added Bootstrap progress bars throughout the application
• Color-Coded Status:
  • 🟢 Green (70%-100%): Key Result is on track or completed
  • 🟡 Yellow (30%-69%): Key Result is progressing but needs attention
  • 🔴 Red (0%-29%): Key Result is behind schedule or just starting

Updated Views

• Add/Edit Forms: Enhanced with percentage input fields and helpful validation messages
• Details View: Shows completion rate with visual progress bar
• Objectives List: Key Results now display completion percentage and mini progress indicators
• Responsive Design: All enhancements work seamlessly with existing Bootstrap 3 styling

Technical Implementation

• Model Updates: Updated all view models to include completion rate tracking
• JavaScript Enhancement: Client-side conversion between user-friendly percentage display and decimal storage
• Comprehensive Testing: Added 11 unit tests covering model validation, view model functionality, and edge cases
• Backward Compatibility: Existing Key Results default to 0% completion, no data loss

Example Usage

// Creating a new Key Result with 75% completion
var keyResult = new KeyResult 
{
    Description = "Increase user engagement by 25%",
    CompletionRate = 0.75m  // 75%
};

The feature provides intuitive visual feedback for tracking OKR progress while maintaining data integrity through proper validation and testing.

Fixes #18.

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