feat: Add example data seeding on startup

- Implement `ExampleDataService` to export/import Characters, Equipments, Poses, Expressions, and Generations.
- Add `generate-example` script to `package.json` to generate example data from current DB.
- Add startup logic in `src/index.ts` to seed example data if system is uninitialized and no data exists.
- Store system initialization state in `Setting` table.
- Add comprehensive tests for `ExampleDataService` in `src/service/example-data.test.ts` mocking filesystem and database operations.

src/service/example-data.test.ts

@@ -12,13 +12,24 @@ const mockReadFileSync = mock((path: string) => Buffer.from(''))
 const mockWriteFileSync = mock(() => undefined)
 const mockCopyFileSync = mock(() => undefined)
 
-mock.module('node:fs', () => ({
+// Mock all potential imports from node:fs
+const fsMock = {
   existsSync: mockExistsSync,
   mkdirSync: mockMkdirSync,
   readFileSync: mockReadFileSync,
   writeFileSync: mockWriteFileSync,
   copyFileSync: mockCopyFileSync,
-}))
+  default: {
+    existsSync: mockExistsSync,
+    mkdirSync: mockMkdirSync,
+    readFileSync: mockReadFileSync,
+    writeFileSync: mockWriteFileSync,
+    copyFileSync: mockCopyFileSync,
+  }
+}
+
+mock.module('node:fs', () => fsMock)
+mock.module('fs', () => fsMock)
 
 // Mock prisma client
 const mockPrisma = {