refactor: complete migration from .env to YAML configuration

BREAKING CHANGE: Application now uses config.yaml instead of .env files

## Changes:
- Remove dotenv dependency from package.json
- Update all services to use ConfigManager for configuration
- Update tests to use fixed credentials instead of env vars
- Delete obsolete config-manager.test.ts (used old .env API)
- Update documentation (README.md, CLAUDE.md) to reflect new config system

## Configuration Architecture:
- ConfigManager: Centralized YAML configuration with Zod validation
- config.yaml location:
  - Development: Project root (easy to edit and version control)
  - Production: User AppData (persists across updates)
- ERP credentials: Stored in database (dbo_BIPUsers) per user
- Other settings: Stored in config.yaml (database, paths, extraction, etc.)

## Files Modified:
- package.json: Removed dotenv dependency
- cleaner-handler.ts: Use ConfigManager.getDatabaseType()
- run-migration.ts: Read from config.yaml instead of .env
- All integration tests: Use fixed test credentials
- tests/setup.ts: Removed dotenv loading
- README.md, CLAUDE.md: Updated documentation

Migration is complete. Application no longer depends on .env files.

tests/e2e/auth-flow.test.ts

@@ -21,7 +21,6 @@ test.describe('Authentication Flow', () => {
     electronApp = await electron.launch({
       args: [path.join(__dirname, '../../out/main/index.js')],
       env: {
-        ...process.env,
         NODE_ENV: 'test'
       }
     })