docs: update all MCP documentation for 22 tools + API key auth

- Rewrite mcp-server/README.md: clean structure, auth section, 22 tools
- Rewrite N8N-CONFIG.md: remove hardcoded IPs, add x-api-key auth flow
- Rewrite N8N-WORKFLOWS.md: simplified, removed AI proxy tool references
- Update README.md/README.fr.md: 37→22 tools, add auth mention
- Update GUIDE.md/GUIDE.en.md: remove AI/API key tool tables, add auth
- Update DEPLOY.md: SSE → Streamable HTTP in architecture diagram

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

DEPLOY.md

@@ -19,7 +19,7 @@ Internet/LAN
      |
      ├── / ──► [memento-web] ── port 3000 ── Next.js App
      |
-     └── /mcp ──► [memento-mcp] ── port 3001 ── MCP Server (SSE)
+     └── /mcp ──► [memento-mcp] ── port 3001 ── MCP Server (Streamable HTTP)
                      |
                   [postgres] ── port 5432 (127.0.0.1 seulement)
 
@@ -246,7 +246,7 @@ server {
         proxy_read_timeout 86400;
     }
 
-    # MCP Server (SSE - long-lived connections)
+    # MCP Server (Streamable HTTP)
     location /mcp {
         proxy_pass http://127.0.0.1:3001/mcp;
         proxy_set_header Host $host;