feat: implement MCP provider registry and service

- Add provider registry to manage LLM providers (Claude, Codex, Cursor, Gemini).
- Create provider routes for MCP server operations (list, upsert, delete, run).
- Implement MCP service for handling server operations and validations.
- Introduce abstract provider class and MCP provider base for shared functionality.
- Add tests for MCP server operations across different providers and scopes.
- Define shared interfaces and types for MCP functionality.
- Implement utility functions for handling JSON config files and API responses.

server/modules/providers/shared/base/abstract.provider.ts

@@ -0,0 +1,14 @@
+import type { IProvider, IProviderMcpRuntime } from '@/shared/interfaces.js';
+import type { LLMProvider } from '@/shared/types.js';
+
+/**
+ * Shared MCP-only provider base.
+ */
+export abstract class AbstractProvider implements IProvider {
+  readonly id: LLMProvider;
+  abstract readonly mcp: IProviderMcpRuntime;
+
+  protected constructor(id: LLMProvider) {
+    this.id = id;
+  }
+}