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/setup.ts

@@ -1,5 +1,4 @@
 import { beforeAll, afterAll, vi } from 'vitest'
-import dotenv from 'dotenv'
 import path from 'path'
 
 // Mock electron app module for unit tests
@@ -12,9 +11,6 @@ vi.mock('electron', () => ({
   }
 }))
 
-// Load environment variables from project root
-dotenv.config({ path: path.resolve(process.cwd(), '.env') })
-
 beforeAll(async () => {
   // Global test setup
   console.log('Test suite starting...')