chore: Move all command handlers to their own files

This makes the code much easier to follow and shortens main.rs from
>1000 lines to around 150.

specs/cli-refactor-plan.md

@@ -223,19 +223,46 @@ COMMANDS:
 - Security audits for data handling
 - Compatibility tests with existing configurations
 
-### Phase 9: File-Based Source Adapters
+### Phase 9.5: Command Handler Extraction ✅ COMPLETED
+
+**Objective**: Extract command handling logic from main.rs into dedicated modules for better maintainability and separation of concerns.
+
+**Steps:**
+1. ✅ Create `commands/` module structure with submodules for each command group
+2. ✅ Extract table printing utilities to `cli/tables.rs`
+3. ✅ Move command handlers to appropriate modules:
+   - `commands/sync.rs`: Sync command logic
+   - `commands/accounts/`: Account management (link, list, status)
+   - `commands/transactions/`: Transaction operations (list, cache, clear)
+   - `commands/list.rs`: Source/destination listing
+4. ✅ Update main.rs to dispatch to new command modules
+5. ✅ Remove extracted functions from main.rs, reducing it from 1049 to ~150 lines
+6. ✅ Update documentation to reflect new structure
+
+**Implementation Details:**
+- Created hierarchical module structure with focused responsibilities
+- Maintained all existing functionality and CLI interface
+- Improved code organization and testability
+- Updated architecture documentation with new module structure
+
+**Testing:**
+- All existing tests pass
+- CLI functionality preserved
+- Code formatting and linting applied
+
+### Phase 10: File-Based Source Adapters
 
 **Objective**: Implement adapters for file-based transaction sources.
 
 **Steps:**
 1. Create `adapters::csv` module implementing `TransactionSource`
-   - Parse CSV files with configurable column mappings
-   - Implement caching similar to GoCardless adapter
-   - Add inspection methods for file status and transaction counts
+    - Parse CSV files with configurable column mappings
+    - Implement caching similar to GoCardless adapter
+    - Add inspection methods for file status and transaction counts
 2. Create `adapters::camt053` and `adapters::mt940` modules
-   - Parse respective financial file formats
-   - Implement transaction mapping and validation
-   - Add format-specific caching and inspection
+    - Parse respective financial file formats
+    - Implement transaction mapping and validation
+    - Add format-specific caching and inspection
 3. Update `adapter_factory` to instantiate file adapters with file paths
 
 **Testing:**