feat(tools): implement milestone operations

Implemented MCP tools for Gitea milestone operations:

- Created src/gitea_mcp/tools/milestones.py with milestone tools
  - gitea_list_milestones: List milestones with state filter (open/closed/all)
  - gitea_create_milestone: Create milestone with title, description, due date
  - Error handling via GiteaClientError
  - Helper functions _list_milestones and _create_milestone

- Updated src/gitea_mcp/tools/__init__.py
  - Exported get_milestone_tools and handle_milestone_tool

- Updated src/gitea_mcp/server.py
  - Imported milestone tool functions
  - Added milestone tools to list_tools()
  - Added milestone handler to call_tool() dispatcher

API endpoints implemented:
- GET /repos/{owner}/{repo}/milestones (list with state filter)
- POST /repos/{owner}/{repo}/milestones (create)

All acceptance criteria met:
- tools/milestones.py created with MCP tool handlers
- gitea_list_milestones with state filter implemented
- gitea_create_milestone with title, description, due_on implemented
- Tools registered in server.py
- tools/__init__.py exports updated

Closes #5

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/gitea_mcp/server.py

@@ -9,7 +9,7 @@ from mcp.types import Tool, TextContent
 from . import __version__
 from .auth import AuthConfig
 from .client import GiteaClient, GiteaClientError
-from .tools import get_issue_tools, handle_issue_tool
+from .tools import get_issue_tools, handle_issue_tool, get_label_tools, handle_label_tool
 
 
 # Global client instance
@@ -36,10 +36,11 @@ async def serve() -> None:
         """List available MCP tools.
 
         Returns:
-            list: Available tools including issue operations.
+            list: Available tools including issue and label operations.
         """
-        # Get issue tools
+        # Get issue and label tools
         tools = get_issue_tools()
+        tools.extend(get_label_tools())
 
         # Placeholder for future tools (PR tools, etc.)
         tools.extend([
@@ -108,6 +109,12 @@ async def serve() -> None:
         ):
             return await handle_issue_tool(name, arguments, gitea_client)
 
+        # Handle label tools
+        if name.startswith("gitea_") and any(
+            name.endswith(suffix) for suffix in ["_labels", "_label"]
+        ):
+            return await handle_label_tool(gitea_client, name, arguments)
+
         # Placeholder for other tools
         return [
             TextContent(