docs: add MCP bearer token authentication guidance

Author: dpolivaev

src/docs/ai/ai-integration-troubleshooting.md

@@ -36,8 +36,11 @@ If another local AI app cannot use Freeplane through MCP:
 - enable `AI MCP server enabled`,
 - check `AI MCP server port`,
 - check `MCP token`,
-- ensure your client sends the token in header
-  `X-Freeplane-MCP-Token`.
+- ensure your client sends the token using one supported header:
+  `Authorization: Bearer <MCP token>` (preferred) or
+  `X-Freeplane-MCP-Token: <MCP token>` (legacy).
+- if your client sends both headers, ensure both token values are
+  identical.
 
 If port is in use, choose another port and restart the server.
 

src/docs/ai/model-context-protocol-server.md

@@ -30,6 +30,12 @@ Open AI Preferences (from the AI panel burger menu), then use:
 3. Set or regenerate `MCP token`.
 4. In your local AI app (for example Claude Desktop or Codex App),
    connect to the Freeplane MCP server using that port and token.
+   Supported authentication headers are:
+   - `Authorization: Bearer <MCP token>` (preferred)
+   - `X-Freeplane-MCP-Token: <MCP token>` (legacy, still supported)
+
+If your client sends both headers, they must contain the same token
+value.
 
 If `MCP token` is empty, Freeplane generates a new token on the first
 incoming client request. That first request is rejected by design. Copy