refactor(repo): consolidate openflare-server to root and move subprojects to internal/apps

- Merge all files inside openflare-server to the repository root directory.
- Relocate agent, relay, and flared subprojects from internal/ to internal/apps/.
- Combine docker-compose files and update build context paths to root.
- Update GitHub workflows and Dockerfiles to refer to new directories and package names.
- Rewrite Go package imports across all files.
- Resolve database renew test race condition and clean up docs.

frontend/lib/services/admin/system-config.service.ts

@@ -0,0 +1,40 @@
+import {BaseService} from '@/lib/services/core';
+import type {CreateSystemConfigRequest, SystemConfig, UpdateSystemConfigRequest,} from './types';
+
+export class AdminSystemConfigService extends BaseService {
+  protected static readonly basePath = '/api/v1/admin';
+
+  static async createSystemConfig(request: CreateSystemConfigRequest): Promise<void> {
+    return this.post<void>('/system-configs', request);
+  }
+
+  static async listSystemConfigs(type?: 'system' | 'business'): Promise<SystemConfig[]> {
+    const query = type ? `?type=${type}` : '';
+    return this.get<SystemConfig[]>(`/system-configs${query}`);
+  }
+
+  static async getSystemConfig(key: string): Promise<SystemConfig> {
+    return this.get<SystemConfig>(`/system-configs/${key}`);
+  }
+
+  static async updateSystemConfig(key: string, request: UpdateSystemConfigRequest): Promise<void> {
+    return this.put<void>(`/system-configs/${key}`, request);
+  }
+
+  static async testSMTP(request: {
+    smtp_host: string;
+    smtp_port: number;
+    smtp_username: string;
+    smtp_password: string;
+    to: string;
+  }): Promise<{ success: boolean; log: string; error: string }> {
+    return this.post<{ success: boolean; log: string; error: string }>(
+      '/system-configs/smtp/test',
+      request,
+    );
+  }
+
+  static async listUploadTypes(): Promise<string[]> {
+    return this.get<string[]>('/uploads/types');
+  }
+}