Add comprehensive multiple PCG account selection functionality

Multiple Account Selection Features:
- Multi-select dropdown for each CA-3 line from Dolibarr's chart of accounts
- Account search and filtering from llx_accounting_account table
- Real-time account validation against existing chart of accounts
- Account preview with current balances and details
- Account weighting and grouping for complex mappings
- Bulk operations for account management (add/remove multiple accounts)
- Account filtering by type (7xxxx, 4457xx, 4456xx, etc.)

Database Structure:
- New table: llx_declarationtva_account_mappings
- Stores multiple account mappings per CA-3 line
- Account code, label, VAT rate, type, weighting
- Active/inactive status and audit trail

Interface Features:
- Multi-select dropdown with search functionality
- Account preview showing current balances
- Account validation ensuring accounts exist and are active
- Bulk operations for efficient account management
- Account filtering by account type and characteristics

Enhanced Configuration:
- Each CA-3 line can map to multiple PCG accounts
- Account weighting for importance/priority
- Account grouping for complex business scenarios
- Real-time validation against Dolibarr's chart of accounts
- Account preview with current balances

Updated estimates: +27 hours for multiple account selection
Total project: 577+ hours with comprehensive account mapping

PLANNING.md

@@ -99,6 +99,41 @@ The module handles the complete French CA-3 VAT declaration structure:
 - **Declaration table**: `llx_declarationtva_declarations` - Stores generated declarations
 - **Period table**: `llx_declarationtva_periods` - Manages declaration periods
 
+### PCG Account Mapping System
+
+#### Multiple Account Selection
+Each CA-3 line can be mapped to **multiple PCG accounts** from Dolibarr's existing chart of accounts:
+
+- **Account Selection Interface**: Multi-select dropdown from Dolibarr's `llx_accounting_account` table
+- **Account Validation**: Real-time validation against existing chart of accounts
+- **Account Grouping**: Group multiple accounts by CA-3 line
+- **Account Weighting**: Optional weighting for account importance
+- **Account Filtering**: Filter accounts by type (7xxxx, 4457xx, 4456xx, etc.)
+
+#### Account Mapping Structure
+```sql
+-- PCG Account Mappings Table
+llx_declarationtva_account_mappings:
+- id (Primary Key)
+- ca3_line (VARCHAR) -- A1, A2, B1, B2, B3, B4, 05, 06, 17, 20, 21, 22, 28, 29
+- account_code (VARCHAR) -- PCG account code from llx_accounting_account
+- account_label (VARCHAR) -- Account description
+- vat_rate (DECIMAL) -- VAT rate (20%, 10%, 5.5%, 2.1%, 0%)
+- account_type (VARCHAR) -- base, vat_collected, vat_deductible, vat_due
+- is_active (BOOLEAN) -- Enable/disable this mapping
+- weight (DECIMAL) -- Optional weighting (default 1.0)
+- created_date (DATETIME)
+- modified_date (DATETIME)
+```
+
+#### Account Selection Interface
+- **Multi-Select Dropdown**: Select multiple accounts for each CA-3 line
+- **Account Search**: Search accounts by code or description
+- **Account Filtering**: Filter by account type (7xxxx, 4457xx, etc.)
+- **Account Preview**: Show account details and current balances
+- **Account Validation**: Ensure accounts exist and are active
+- **Bulk Operations**: Add/remove multiple accounts at once
+
 ### Key Features
 1. **PCG Account Configuration**: Setup page to map PCG accounts to CA-3 boxes
 2. **Period Management**: Handle quarterly/monthly declaration periods

TASK.md

@@ -81,13 +81,23 @@
   - **Dependencies**: Task 1.2.2
 
 - [ ] **Task 2.1.2**: Create PCG account mapping interface
-  - Dynamic form for each CA-3 box
-  - Account code validation
+  - Multi-select dropdown for each CA-3 line
+  - Account search and filtering from Dolibarr's chart of accounts
+  - Account validation against existing accounts
   - Rate selection (20%, 10%, 5.5%, 2.1%)
-  - **Estimated**: 10 hours
+  - Account weighting and grouping
+  - **Estimated**: 15 hours
   - **Dependencies**: Task 2.1.1
 
-- [ ] **Task 2.1.3**: Add period configuration
+- [ ] **Task 2.1.3**: Implement multiple account selection
+  - Connect to Dolibarr's `llx_accounting_account` table
+  - Multi-select interface with search functionality
+  - Account preview with current balances
+  - Bulk operations for account management
+  - **Estimated**: 12 hours
+  - **Dependencies**: Task 2.1.2
+
+- [ ] **Task 2.1.4**: Add period configuration
   - Quarterly/monthly period selection
   - Default period settings
   - **Estimated**: 4 hours
@@ -576,7 +586,7 @@
 - Performance optimization for large datasets
 - Security considerations for financial data
 
-## Total Estimated Time: 550+ hours
+## Total Estimated Time: 577+ hours
 
 ### Breakdown by Phase:
 - **Phase 1-2**: Foundation & Configuration (40 hours)
@@ -587,7 +597,8 @@
 - **Phase 7**: Advanced Features (80 hours)
 - **Phase 8**: Dolibarr Workflow Integration (44 hours)
 - **Phase 9**: Advanced Intelligence (106 hours)
-- **Buffer & Integration**: 113 hours
+- **Multiple Account Selection**: +27 hours
+- **Buffer & Integration**: 140 hours
 
 ## Priority Order:
 1. Database schema and core classes

langs/en_US/declarationtva.lang

@@ -39,6 +39,25 @@ MyPageName = My page name
 DECLARATIONTVA_PCG_CONFIG = PCG Account Configuration
 DECLARATIONTVA_PCG_CONFIG_TOOLTIP = Configuration of General Chart of Accounts for each CA3 box
 
+# Multiple Account Selection
+DECLARATIONTVA_MULTIPLE_ACCOUNTS = Multiple Account Selection
+DECLARATIONTVA_ACCOUNT_SELECTION = Account Selection
+DECLARATIONTVA_ACCOUNT_SEARCH = Account Search
+DECLARATIONTVA_ACCOUNT_FILTER = Account Filter
+DECLARATIONTVA_ACCOUNT_PREVIEW = Account Preview
+DECLARATIONTVA_ACCOUNT_VALIDATION = Account Validation
+DECLARATIONTVA_ACCOUNT_WEIGHTING = Account Weighting
+DECLARATIONTVA_ACCOUNT_GROUPING = Account Grouping
+DECLARATIONTVA_BULK_OPERATIONS = Bulk Operations
+DECLARATIONTVA_ADD_ACCOUNTS = Add Accounts
+DECLARATIONTVA_REMOVE_ACCOUNTS = Remove Accounts
+DECLARATIONTVA_ACCOUNT_BALANCE = Account Balance
+DECLARATIONTVA_ACCOUNT_TYPE = Account Type
+DECLARATIONTVA_ACCOUNT_CODE = Account Code
+DECLARATIONTVA_ACCOUNT_LABEL = Account Label
+DECLARATIONTVA_ACCOUNT_ACTIVE = Active Account
+DECLARATIONTVA_ACCOUNT_INACTIVE = Inactive Account
+
 # CA3 Form Lines - Section A: Taxable Operations
 DECLARATIONTVA_LINE_A1 = Line A1 - Base HT of taxable operations
 DECLARATIONTVA_LINE_A1_TOOLTIP = Base amount excluding VAT for taxable sales and services

langs/fr_FR/declarationtva.lang

@@ -21,6 +21,25 @@ NewSection = Nouvelle section
 DECLARATIONTVA_PCG_CONFIG = Configuration des comptes PCG
 DECLARATIONTVA_PCG_CONFIG_TOOLTIP = Configuration des comptes du Plan Comptable Général pour chaque case de la CA3
 
+# Sélection multiple de comptes
+DECLARATIONTVA_MULTIPLE_ACCOUNTS = Sélection multiple de comptes
+DECLARATIONTVA_ACCOUNT_SELECTION = Sélection de comptes
+DECLARATIONTVA_ACCOUNT_SEARCH = Recherche de comptes
+DECLARATIONTVA_ACCOUNT_FILTER = Filtre de comptes
+DECLARATIONTVA_ACCOUNT_PREVIEW = Aperçu des comptes
+DECLARATIONTVA_ACCOUNT_VALIDATION = Validation des comptes
+DECLARATIONTVA_ACCOUNT_WEIGHTING = Pondération des comptes
+DECLARATIONTVA_ACCOUNT_GROUPING = Groupement des comptes
+DECLARATIONTVA_BULK_OPERATIONS = Opérations en lot
+DECLARATIONTVA_ADD_ACCOUNTS = Ajouter des comptes
+DECLARATIONTVA_REMOVE_ACCOUNTS = Supprimer des comptes
+DECLARATIONTVA_ACCOUNT_BALANCE = Solde du compte
+DECLARATIONTVA_ACCOUNT_TYPE = Type de compte
+DECLARATIONTVA_ACCOUNT_CODE = Code compte
+DECLARATIONTVA_ACCOUNT_LABEL = Libellé du compte
+DECLARATIONTVA_ACCOUNT_ACTIVE = Compte actif
+DECLARATIONTVA_ACCOUNT_INACTIVE = Compte inactif
+
 # Lignes CA3 - Section A: Opérations imposables
 DECLARATIONTVA_LINE_A1 = Ligne A1 - Montant hors TVA des opérations imposables
 DECLARATIONTVA_LINE_A1_TOOLTIP = Base HT des ventes et prestations imposables