fix(mcp): convert PromptArgument types in prompts/list MCP handler (#3953)

* fix: convert PromptArgument types in prompts/list MCP handler

Fixes #3939

The prompts/list MCP JSON-RPC method was returning empty arrays due to
a Pydantic v2 type validation error. The root cause was a type mismatch
between mcpgateway.schemas.PromptArgument (from the database layer) and
mcp.types.PromptArgument (expected by the MCP SDK).

Changes:
- Add explicit type conversion in list_prompts() for both code paths
  (with and without server_id) to convert schema PromptArgument to
  MCP PromptArgument by mapping name, description, and required fields
- Update test to use mcpgateway.schemas.PromptArgument instead of
  mcp.types.PromptArgument to properly test the conversion
- Fix test data to use required=True instead of required=None

The fix ensures MCP clients receive valid prompt lists through
/servers/{UUID}/mcp/ and /mcp/ endpoints.

Signed-off-by: Bogdan-Marius-Catanus <bogdan-marius.catanus@ibm.com>
Signed-off-by: Mihai Criveti <crivetimihai@gmail.com>

* chore: update secrets baseline

Signed-off-by: Mihai Criveti <crivetimihai@gmail.com>

---------

Signed-off-by: Bogdan-Marius-Catanus <bogdan-marius.catanus@ibm.com>
Signed-off-by: Mihai Criveti <crivetimihai@gmail.com>
Co-authored-by: Bogdan-Marius-Catanus <bogdan-marius.catanus@ibm.com>
Co-authored-by: Mihai Criveti <crivetimihai@gmail.com>

Author: 3 people

.secrets.baseline

@@ -3,7 +3,7 @@
     "files": "package-lock.json|Cargo.lock|^.secrets.baseline$|scripts/sign_image.sh|scripts/zap|sonar-project.properties|^/Users/brian/dev/github.ibm.com/contextforge-org/sps-pipeline-config/.secrets.baseline$|^./.secrets.baseline$",
     "lines": null
   },
-  "generated_at": "2026-04-04T15:50:18Z",
+  "generated_at": "2026-04-04T22:57:41Z",
   "plugins_used": [
     {
       "name": "AWSKeyDetector"
@@ -11028,15 +11028,15 @@
         "hashed_secret": "b4c9248600a42f8c38c01b632f392dbcb4c7b19a",
         "is_secret": false,
         "is_verified": false,
-        "line_number": 11072,
+        "line_number": 11073,
         "type": "Hex High Entropy String",
         "verified_result": null
       },
       {
         "hashed_secret": "90bd1b48e958257948487b90bee080ba5ed00caa",
         "is_secret": false,
         "is_verified": false,
-        "line_number": 12209,
+        "line_number": 12210,
         "type": "Hex High Entropy String",
         "verified_result": null
       }

tests/unit/mcpgateway/transports/test_streamablehttp_transport.py

@@ -849,6 +849,7 @@ async def fake_get_db():
     assert len(result[0].arguments) == 1
     assert isinstance(result[0].arguments[0], PromptArgument)
     assert result[0].arguments[0].name == "arg1"
+    assert result[0].arguments[0].required is False
 
 
 @pytest.mark.asyncio