Refactor MCP resources to tools, add chat deletion

This commit implements two main changes based on your feedback:

1.  Refactors all Model Context Protocol (MCP) resources into tools:
    - In `whatsappIntegration.js`:
        - `whatsapp.chat` (resource) -> `whatsapp.list-chats` (tool) & `whatsapp.get-chat-details` (tool)
        - `whatsapp.contact` (resource) -> `whatsapp.get-contact-details` (tool)
        - `whatsapp.blocklist` (resource) -> `whatsapp.get-blocklist` (tool)
    - In `conversationIntegration.js`:
        - `conversation` (resource) -> `conversation.list-conversations` (tool) & `conversation.get-conversation-details` (tool)
    This change aligns with current Gemini SDK capabilities for MCP.

2.  Implements chat deletion functionality:
    - In `whatsapp-router`:
        - Added `deleteChat` function to `whatsappClient.ts`. This function calls an assumed OpenWA endpoint (`POST /deleteChat`) and will require verification against the actual OpenWA API.
        - Added a `DELETE /chats/:chatId` route to `whatsappActions.ts` that utilizes the new `deleteChat` client function.
    - In `conversation-layer-mcp`:
        - Added a new `whatsapp.delete-chat` tool to `whatsappIntegration.js`. This tool calls the new `DELETE /chats/:chatId` endpoint in `whatsapp-router`.

Additionally, the existing `conversation.delete` MCP tool was verified to be correctly implemented.

mcp/lib/api.js

@@ -1,4 +1,9 @@
-export const API_BASE_URL = process.env.PLANILLA_API_URL || "http://localhost:4000";
+export const API_BASE_URL = process.env.WHATSAPP_ROUTER_URL;
+
+if (!API_BASE_URL) {
+  console.error("FATAL: WHATSAPP_ROUTER_URL environment variable is not set.");
+  process.exit(1);
+}
 
 export async function fetchJSON(path, options = {}) {
   const method = options.method || "GET";