feat: add missing administration tools

Add 20+ new MCP tools for repository administration:

- Repository: get_repo, repo_write (edit/delete/transfer), list_forks
- Branch Protection: read (list/get) and write (create/edit/delete)
- Webhooks: read (list/get) and write (create/edit/delete/test)
- Collaborators: read (list) and write (add/delete)
- Deploy Keys: read (list/get) and write (create/delete)
- Topics: read (list) and write (add/delete/set)
- Compare: get_compare for branch/tag/commit comparison
- Organization: org_read (get/list_teams/get_team/list_team_members/list_team_repos)
  and org_write (create_team/delete_team/add_team_member/remove_team_member/add_team_repo/remove_team_repo)
- PR enhancements: list_files and is_merged methods added to pull_request_read

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

operation/repo/compare.go

@@ -0,0 +1,59 @@
+package repo
+
+import (
+	"context"
+	"fmt"
+
+	"gitea.com/gitea/gitea-mcp/pkg/gitea"
+	"gitea.com/gitea/gitea-mcp/pkg/log"
+	"gitea.com/gitea/gitea-mcp/pkg/params"
+	"gitea.com/gitea/gitea-mcp/pkg/to"
+
+	"github.com/mark3labs/mcp-go/mcp"
+	"github.com/mark3labs/mcp-go/server"
+)
+
+const (
+	GetCompareToolName = "get_compare"
+)
+
+var (
+	GetCompareTool = mcp.NewTool(
+		GetCompareToolName,
+		mcp.WithDescription("Compare two branches, tags, or commits. Returns commits and diff stats between the base and head."),
+		mcp.WithString("owner", mcp.Required(), mcp.Description("repository owner")),
+		mcp.WithString("repo", mcp.Required(), mcp.Description("repository name")),
+		mcp.WithString("basehead", mcp.Required(), mcp.Description("comparison in format 'base...head' (e.g. 'main...feature-branch')")),
+	)
+)
+
+func init() {
+	Tool.RegisterRead(server.ServerTool{
+		Tool:    GetCompareTool,
+		Handler: getCompareFn,
+	})
+}
+
+func getCompareFn(ctx context.Context, req mcp.CallToolRequest) (*mcp.CallToolResult, error) {
+	log.Debugf("Called getCompareFn")
+	args := req.GetArguments()
+	owner, err := params.GetString(args, "owner")
+	if err != nil {
+		return to.ErrorResult(err)
+	}
+	repo, err := params.GetString(args, "repo")
+	if err != nil {
+		return to.ErrorResult(err)
+	}
+	basehead, err := params.GetString(args, "basehead")
+	if err != nil {
+		return to.ErrorResult(err)
+	}
+
+	var result map[string]any
+	_, err = gitea.DoJSON(ctx, "GET", fmt.Sprintf("repos/%s/%s/compare/%s", owner, repo, basehead), nil, nil, &result)
+	if err != nil {
+		return to.ErrorResult(fmt.Errorf("compare %v in %v/%v err: %v", basehead, owner, repo, err))
+	}
+	return to.TextResult(result)
+}