Update TASK.md with completed MVP work

Updated:
- Phase 1.5: MVP Implementation & Bug Fixes - COMPLETED
- Phase 2: Configuration Interface - COMPLETED
- Phase 3: Data Processing - COMPLETED
- Added new tasks for calculation engine, subtotals, Section D logic
- Added tasks for VAT rounding and display formatting
- All MVP core functionality now marked as completed
- Ready for next phase development

TASK.md

@@ -108,9 +108,47 @@
   - **Estimated**: 1 hour
   - **Dependencies**: Task 1.5.4
 
+### 1.5.3 MVP Calculation Engine & Display ✅ **COMPLETED**
+- [x] **Task 1.5.6**: Implement CA-3 calculation engine ✅ **COMPLETED**
+  - Complete CA-3 form structure (Notice 4722 - 3310-CA3-SD)
+  - Section A: Opérations imposables (A1-A5)
+  - Section B: TVA due (08, 09, 9B, 17)
+  - Section C: TVA déductible (20, 21, 22)
+  - Section D: Résultat (25, 26, TD, 28, 29)
+  - **Estimated**: 20 hours
+  - **Dependencies**: Task 1.5.5
+
+- [x] **Task 1.5.7**: Add subtotal lines for user reference ✅ **COMPLETED**
+  - Line 16: Subtotal TVA due (08 + 09 + 9B)
+  - Line 23: Subtotal TVA déductible (20 + 21 + 22)
+  - Automatic calculation and display
+  - **Estimated**: 4 hours
+  - **Dependencies**: Task 1.5.6
+
+- [x] **Task 1.5.8**: Fix Section D calculation logic ✅ **COMPLETED**
+  - Line 25: Only shows value if VAT credit (negative result)
+  - Line TD: Only shows value if VAT due (positive result)
+  - Clear separation between payment and receipt scenarios
+  - **Estimated**: 6 hours
+  - **Dependencies**: Task 1.5.6
+
+- [x] **Task 1.5.9**: Implement VAT amount rounding ✅ **COMPLETED**
+  - Round all VAT amounts to whole numbers
+  - Display original amounts in brackets for transparency
+  - Store both rounded and original values
+  - **Estimated**: 8 hours
+  - **Dependencies**: Task 1.5.8
+
+- [x] **Task 1.5.10**: Clean up display formatting ✅ **COMPLETED**
+  - Display rounded values without decimals
+  - Show empty fields for zero values
+  - Original amounts only where needed (data lines)
+  - **Estimated**: 4 hours
+  - **Dependencies**: Task 1.5.9
+
 ---
 
-## Phase 2: Configuration Interface (Week 3-4)
+## Phase 2: Configuration Interface (Week 3-4) ✅ **COMPLETED**
 
 ### 2.1 Setup Page Enhancement
 - [x] **Task 2.1.1**: Redesign admin setup page ✅ **COMPLETED**
@@ -137,21 +175,21 @@
   - **Estimated**: 12 hours
   - **Dependencies**: Task 2.1.2
 
-- [ ] **Task 2.1.4**: Add period configuration
+- [x] **Task 2.1.4**: Add period configuration ✅ **COMPLETED**
   - Quarterly/monthly period selection
   - Default period settings
   - **Estimated**: 4 hours
   - **Dependencies**: Task 1.2.3
 
 ### 2.2 User Interface Components
-- [ ] **Task 2.2.1**: Create main declaration interface
+- [x] **Task 2.2.1**: Create main declaration interface ✅ **COMPLETED**
   - File: `declarationtvaindex.php`
   - Period selection dropdown
   - Declaration status display
   - **Estimated**: 6 hours
   - **Dependencies**: Task 1.2.1
 
-- [ ] **Task 2.2.2**: Add declaration creation wizard
+- [x] **Task 2.2.2**: Add declaration creation wizard ✅ **COMPLETED**
   - Step-by-step process
   - Data validation at each step
   - **Estimated**: 8 hours
@@ -159,17 +197,17 @@
 
 ---
 
-## Phase 3: Data Processing (Week 5-6)
+## Phase 3: Data Processing (Week 5-6) ✅ **COMPLETED**
 
 ### 3.1 Accounting Data Extraction
-- [ ] **Task 3.1.1**: Create data extraction methods
+- [x] **Task 3.1.1**: Create data extraction methods ✅ **COMPLETED**
   - Query Dolibarr accounting tables
   - Filter by PCG account codes
   - Handle different VAT rates
   - **Estimated**: 12 hours
   - **Dependencies**: Task 1.2.1
 
-- [ ] **Task 3.1.2**: Implement CA-3 calculation logic
+- [x] **Task 3.1.2**: Implement CA-3 calculation logic ✅ **COMPLETED**
   - Section A (Output VAT): Boxes 01, 02, 03, 05, 08
   - Section B (Input VAT): Boxes 20, 21, 22
   - Section C (Result): Boxes 25, 26, 28, 29