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/shared/types.ts

@@ -0,0 +1,70 @@
+// -------------- HTTP API response shapes for the server, shared across modules --------------
+
+export type ApiSuccessShape<TData = unknown> = {
+  success: true;
+  data: TData;
+};
+
+export type ApiErrorShape = {
+  success: false;
+  error: {
+    code: string;
+    message: string;
+    details?: unknown;
+  };
+};
+
+// ---------------------------------------------------------------------------------------------
+
+export type LLMProvider = 'claude' | 'codex' | 'gemini' | 'cursor';
+
+// ---------------------------------------------------------------------------------------------
+
+export type AppErrorOptions = {
+  code?: string;
+  statusCode?: number;
+  details?: unknown;
+};
+
+// -------------------- MCP related shared types --------------------
+export type McpScope = 'user' | 'local' | 'project';
+
+export type McpTransport = 'stdio' | 'http' | 'sse';
+
+/**
+ * Provider MCP server descriptor normalized for frontend consumption.
+ */
+export type ProviderMcpServer = {
+  provider: LLMProvider;
+  name: string;
+  scope: McpScope;
+  transport: McpTransport;
+  command?: string;
+  args?: string[];
+  env?: Record<string, string>;
+  cwd?: string;
+  url?: string;
+  headers?: Record<string, string>;
+  envVars?: string[];
+  bearerTokenEnvVar?: string;
+  envHttpHeaders?: Record<string, string>;
+};
+
+/**
+ * Shared payload shape for MCP server create/update operations.
+ */
+export type UpsertProviderMcpServerInput = {
+  name: string;
+  scope?: McpScope;
+  transport: McpTransport;
+  workspacePath?: string;
+  command?: string;
+  args?: string[];
+  env?: Record<string, string>;
+  cwd?: string;
+  url?: string;
+  headers?: Record<string, string>;
+  envVars?: string[];
+  bearerTokenEnvVar?: string;
+  envHttpHeaders?: Record<string, string>;
+};