feat(web): add list-apps-detailed endpoint

Merge https://github.com/google/adk-python/pull/3430

**Please ensure you have read the [contribution guide](https://github.com/google/adk-python/blob/main/CONTRIBUTING.md) before creating a pull request.**

### Link to Issue or Description of Change

**1. Link to an existing issue (if applicable):**

- Closes: #3429

**2. Or, if no issue exists, describe the change:**

_If applicable, please follow the issue templates to provide as much detail as
possible._

**Problem:**
The existing `/list-apps` endpoint only returns the name of the folder that each agent is in

**Solution:**
This adds a new endpoint `/list-apps-detailed` which will load each agent using the existing `AgentLoader.load_agent` method, and then return the folder name, display name (with underscores replaced with spaces for a more readable version), description, and the agent type.

This does introduce overhead if you had multiple agents since they all need to be loaded, but by maintaining the existing `/list-apps` endpoint, users can choose which one to hit if they don't want to load all agents. Since the existing `load_agents` method will cache results, there's only a penalty on the first hit.

### Testing Plan

Created a unit test for this, similar to the `/list-apps`. Also tested this with my own ADK instance to verify it loaded correctly.
```
curl --location "localhost:8000/list-apps-detailed"
```
```json
{
    "apps": [
        {
            "name": "agent_1",
            "displayName": "Agent 1",
            "description": "A test description for a test agent",
            "agentType": "package"
        },
        {
            "name": "agent_2",
            "displayName": "Agent 2",
            "description": "A test description for a test agent ",
            "agentType": "package"
        },
        {
            "name": "agent_3",
            "displayName": "Agent 3",
            "description": "A test description for a test agent",
            "agentType": "package"
        }
    ]
}

```

**Unit Tests:**

- [X] I have added or updated unit tests for my change.
- [X] All unit tests pass locally.

 3054 passed, 2383 warnings in 46.96s

### Checklist

- [X] I have read the [CONTRIBUTING.md](https://github.com/google/adk-python/blob/main/CONTRIBUTING.md) document.
- [X] I have performed a self-review of my own code.
- [X] I have commented my code, particularly in hard-to-understand areas.
- [X] I have added tests that prove my fix is effective or that my feature works.
- [X] New and existing unit tests pass locally with my changes.
- [X] I have manually tested my changes end-to-end.
- [X] Any dependent changes have been merged and published in downstream modules.

COPYBARA_INTEGRATE_REVIEW=https://github.com/google/adk-python/pull/3430 from dylan-apex:more-detailed-list-apps e6864fd61a673da5fd2fb28d2d7d72cb90f5af0a
PiperOrigin-RevId: 834907771

tests/unittests/cli/test_fast_api.py

@@ -190,6 +190,14 @@ def mock_agent_loader():
     def list_agents(self):
       return ["test_app"]
 
+    def list_agents_detailed(self):
+      return [{
+          "name": "test_app",
+          "root_agent_name": "test_agent",
+          "description": "A test agent for unit testing",
+          "language": "python",
+      }]
+
   return MockAgentLoader(".")
 
 
@@ -548,6 +556,26 @@ def test_list_apps(test_app):
   logger.info(f"Listed apps: {data}")
 
 
+def test_list_apps_detailed(test_app):
+  """Test listing available applications with detailed metadata."""
+  response = test_app.get("/list-apps?detailed=true")
+
+  assert response.status_code == 200
+  data = response.json()
+  assert isinstance(data, dict)
+  assert "apps" in data
+  assert isinstance(data["apps"], list)
+
+  for app in data["apps"]:
+    assert "name" in app
+    assert "rootAgentName" in app
+    assert "description" in app
+    assert "language" in app
+    assert app["language"] in ["yaml", "python"]
+
+  logger.info(f"Listed apps: {data}")
+
+
 def test_create_session_with_id(test_app, test_session_info):
   """Test creating a session with a specific ID."""
   new_session_id = "new_session_id"