[Feat]: a "no SSL" configuration

### Is your feature request related to a problem? Please describe.

I'm querying a A2A endpoint with http:// (no SSL, as it's a non prod deployment), but it seems it is not supported, or did I miss it?

Right now, the UI displays:
```
Error: An internal server error occurred: HTTP Error 503: Network communication error fetching agent card from https://localhost:5601/api/agent_builder/a2a/docs-agent.json: [SSL: WRONG_VERSION_NUMBER] wrong version number (_ssl.c:1028)
```

I'm getting this log:
```
[BACKEND] 2025-11-26 14:54:30,463 - app - ERROR - An internal server error occurred
[BACKEND] Traceback (most recent call last):
[BACKEND] File "/Users/vincent/installs/agent-builder-demo/a2a-inspector/.venv/lib/python3.13/site-packages/httpx/_transports/default.py", line 101, in map_httpcore_exceptions
[BACKEND] yield
[BACKEND] File "/Users/vincent/installs/agent-builder-demo/a2a-inspector/.venv/lib/python3.13/site-packages/httpx/_transports/default.py", line 394, in handle_async_request
[BACKEND] resp = await self._pool.handle_async_request(req)
[BACKEND] ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[BACKEND] File "/Users/vincent/installs/agent-builder-demo/a2a-inspector/.venv/lib/python3.13/site-packages/httpcore/_async/connection_pool.py", line 256, in handle_async_request
[BACKEND] raise exc from None
[BACKEND] File "/Users/vincent/installs/agent-builder-demo/a2a-inspector/.venv/lib/python3.13/site-packages/httpcore/_async/connection_pool.py", line 236, in handle_async_request
[BACKEND] response = await connection.handle_async_request(
[BACKEND] ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[BACKEND] pool_request.request
[BACKEND] ^^^^^^^^^^^^^^^^^^^^
[BACKEND] )
[BACKEND] ^
[BACKEND] File "/Users/vincent/installs/agent-builder-demo/a2a-inspector/.venv/lib/python3.13/site-packages/httpcore/_async/connection.py", line 101, in handle_async_request
[BACKEND] raise exc
[BACKEND] File "/Users/vincent/installs/agent-builder-demo/a2a-inspector/.venv/lib/python3.13/site-packages/httpcore/_async/connection.py", line 78, in handle_async_request
[BACKEND] stream = await self._connect(request)
[BACKEND] ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[BACKEND] File "/Users/vincent/installs/agent-builder-demo/a2a-inspector/.venv/lib/python3.13/site-packages/httpcore/_async/connection.py", line 156, in _connect
[BACKEND] stream = await stream.start_tls(**kwargs)
[BACKEND] ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
[BACKEND] File "/Users/vincent/installs/agent-builder-demo/a2a-inspector/.venv/lib/python3.13/site-packages/httpcore/_backends/anyio.py", line 67, in start_tls
[BACKEND] with map_exceptions(exc_map):
[BACKEND] ~~~~~~~~~~~~~~^^^^^^^^^
[BACKEND] File "/Library/Frameworks/Python.framework/Versions/3.13/lib/python3.13/contextlib.py", line 162, in __exit__
[BACKEND] self.gen.throw(value)
[BACKEND] ~~~~~~~~~~~~~~^^^^^^^
[BACKEND] File "/Users/vincent/installs/agent-builder-demo/a2a-inspector/.venv/lib/python3.13/site-packages/httpcore/_exceptions.py", line 14, in map_exceptions
[BACKEND] raise to_exc(exc) from exc
[BACKEND] httpcore.ConnectError: [SSL: WRONG_VERSION_NUMBER] wrong version number (_ssl.c:1028)
```

### Describe the solution you'd like

Have a config flag to enable https

### Describe alternatives you've considered

_No response_

### Additional context

_No response_

### Code of Conduct

- [x] I agree to follow this project's Code of Conduct

The error trace shows an SSL issue when connecting to an HTTP endpoint. Look at the backend code handling A2A agent card fetching, likely in a Python file using httpx/httpcore. Find where the URL is constructed or where SSL verification is enforced. The feature is to add a configuration flag to allow HTTP connections. Check for existing configuration files and how they are read. Test by running the inspector against a local HTTP endpoint.

Vom Indexierungsmodell aus dem Issue-Text verfasst.