test: improve test coverage from 61% to 84.81%

Major improvements:
- Fixed all 42 broken tests (database connection leaks)
- Added db_connection() context manager for proper cleanup
- Created comprehensive test suites for undertested modules

New test coverage:
- tools/general_tools.py: 26 tests (97% coverage)
- tools/price_tools.py: 11 tests (validates NASDAQ symbols, date handling)
- api/price_data_manager.py: 12 tests (85% coverage)
- api/routes/results_v2.py: 3 tests (98% coverage)
- agent/reasoning_summarizer.py: 2 tests (87% coverage)
- api/routes/period_metrics.py: 2 edge case tests (100% coverage)
- agent/mock_provider: 1 test (100% coverage)

Database fixes:
- Added db_connection() context manager to prevent leaks
- Updated 16+ test files to use context managers
- Fixed drop_all_tables() to match new schema
- Added CHECK constraint for action_type
- Added ON DELETE CASCADE to trading_days foreign key

Test improvements:
- Updated SQL INSERT statements with all required fields
- Fixed date parameter handling in API integration tests
- Added edge case tests for validation functions
- Fixed import errors across test suite

Results:
- Total coverage: 84.81% (was 61%)
- Tests passing: 406 (was 364 with 42 failures)
- Total lines covered: 6364 of 7504

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

scripts/fix_db_connections.py

@@ -0,0 +1,108 @@
+#!/usr/bin/env python3
+"""
+Script to convert database connection usage to context managers.
+
+Converts patterns like:
+    conn = get_db_connection(path)
+    # code
+    conn.close()
+
+To:
+    with db_connection(path) as conn:
+        # code
+"""
+
+import re
+import sys
+from pathlib import Path
+
+
+def fix_test_file(filepath):
+    """Convert get_db_connection to db_connection context manager."""
+    print(f"Processing: {filepath}")
+
+    with open(filepath, 'r') as f:
+        content = f.read()
+
+    original_content = content
+
+    # Step 1: Add db_connection to imports if needed
+    if 'from api.database import' in content and 'db_connection' not in content:
+        # Find the import statement
+        import_pattern = r'(from api\.database import \([\s\S]*?\))'
+        match = re.search(import_pattern, content)
+
+        if match:
+            old_import = match.group(1)
+            # Add db_connection after get_db_connection
+            new_import = old_import.replace(
+                'get_db_connection,',
+                'get_db_connection,\n    db_connection,'
+            )
+            content = content.replace(old_import, new_import)
+            print("  ✓ Added db_connection to imports")
+
+    # Step 2: Convert simple patterns (conn = get_db_connection ... conn.close())
+    # This is a simplified version - manual review still needed
+    content = content.replace(
+        'conn = get_db_connection(',
+        'with db_connection('
+    )
+    content = content.replace(
+        ') as conn:',
+        ') as conn:'  # No-op to preserve existing context managers
+    )
+
+    # Note: We still need manual fixes for:
+    # 1. Adding proper indentation
+    # 2. Removing conn.close() statements
+    # 3. Handling cursor patterns
+
+    if content != original_content:
+        with open(filepath, 'w') as f:
+            f.write(content)
+        print(f"  ✓ Updated {filepath}")
+        return True
+    else:
+        print(f"  - No changes needed for {filepath}")
+        return False
+
+
+def main():
+    test_dir = Path(__file__).parent.parent / 'tests'
+
+    # List of test files to update
+    test_files = [
+        'unit/test_database.py',
+        'unit/test_job_manager.py',
+        'unit/test_database_helpers.py',
+        'unit/test_price_data_manager.py',
+        'unit/test_model_day_executor.py',
+        'unit/test_trade_tools_new_schema.py',
+        'unit/test_get_position_new_schema.py',
+        'unit/test_cross_job_position_continuity.py',
+        'unit/test_job_manager_duplicate_detection.py',
+        'unit/test_dev_database.py',
+        'unit/test_database_schema.py',
+        'unit/test_model_day_executor_reasoning.py',
+        'integration/test_duplicate_simulation_prevention.py',
+        'integration/test_dev_mode_e2e.py',
+        'integration/test_on_demand_downloads.py',
+        'e2e/test_full_simulation_workflow.py',
+    ]
+
+    updated_count = 0
+    for test_file in test_files:
+        filepath = test_dir / test_file
+        if filepath.exists():
+            if fix_test_file(filepath):
+                updated_count += 1
+        else:
+            print(f"  ⚠ File not found: {filepath}")
+
+    print(f"\n✓ Updated {updated_count} files")
+    print("⚠ Manual review required - check indentation and remove conn.close() calls")
+
+
+if __name__ == '__main__':
+    main()