Replace state blob with resource-oriented API endpoints

Split /api/v1/state into dedicated resource endpoints:
- /api/v1/operator, /api/v1/central-domain
- /api/v1/ddns/config, /api/v1/dns/settings
- /api/v1/dhcp/config (moved from /dnsmasq/dhcp/)
- /api/v1/nftables/config, /api/v1/haproxy/routes

Each page now talks to its own resource instead of deep-merging
a blob. Removes useConfig hook, CentralState type, and legacy
config methods.

web/src/services/api-legacy.ts

@@ -1,7 +1,5 @@
 import type {
   Status,
-  CentralState,
-  CentralStateResponse,
   HealthResponse,
   StatusResponse,
   NetworkInfo,
@@ -30,16 +28,6 @@ class ApiService {
     return response.json();
   }
 
-  private async requestText(endpoint: string, options?: RequestInit): Promise<string> {
-    const url = `${this.baseUrl}${endpoint}`;
-    const response = await fetch(url, options);
-    
-    if (!response.ok) {
-      throw new Error(`HTTP error! status: ${response.status}`);
-    }
-    
-    return response.text();
-  }
 
   async getStatus(): Promise<Status> {
     return this.request<Status>('/api/status');
@@ -49,43 +37,6 @@ class ApiService {
     return this.request<HealthResponse>('/api/v1/health');
   }
 
-  // ========================================
-  // Global Config APIs (Wild Central level)
-  // Endpoint: /api/v1/state
-  // ========================================
-
-  async getConfig(): Promise<CentralStateResponse> {
-    return this.request<CentralStateResponse>('/api/v1/state');
-  }
-
-  async getConfigYaml(): Promise<string> {
-    return this.requestText('/api/v1/state/yaml');
-  }
-
-  async updateConfigYaml(yamlContent: string): Promise<StatusResponse> {
-    return this.request<StatusResponse>('/api/v1/state/yaml', {
-      method: 'PUT',
-      headers: { 'Content-Type': 'text/plain' },
-      body: yamlContent
-    });
-  }
-
-  async createConfig(config: CentralState): Promise<StatusResponse> {
-    return this.request<StatusResponse>('/api/v1/state', {
-      method: 'POST',
-      headers: { 'Content-Type': 'application/json' },
-      body: JSON.stringify(config)
-    });
-  }
-
-  async updateConfig(config: CentralState): Promise<StatusResponse> {
-    return this.request<StatusResponse>('/api/v1/state', {
-      method: 'PUT',
-      headers: { 'Content-Type': 'application/json' },
-      body: JSON.stringify(config)
-    });
-  }
-
   async getDnsmasqStatus(): Promise<DnsmasqStatus> {
     return this.request<DnsmasqStatus>('/api/v1/dnsmasq/status');
   }