feat: issue_list + workflow_run_list tools (#28, #29)

Adds the *_list partners that the existing *_get tools have been
missing. Same pattern as repo_list — owner allowlisted, capLimit
helper for pagination, next_page surfaced when the page is full.

internal/gitea/issues.go:
- ListIssues(owner, repo, args) hitting
  GET /api/v1/repos/{owner}/{repo}/issues with type=issues server-side
  so PRs don't leak in (gitea conflates them on this endpoint).
- ListIssuesArgs struct: State, Labels, Since (ISO 8601), Page, Limit.

internal/gitea/workflows.go:
- ListWorkflowRuns(owner, repo, args) hitting
  GET /api/v1/repos/{owner}/{repo}/actions/runs.
- Expanded WorkflowRun struct with DisplayTitle, Event, HeadSHA,
  HeadBranch, WorkflowID, RunNumber, UpdatedAt, Actor so callers
  can pin runs to a commit / branch without a second lookup.
- ListWorkflowRunsArgs: Branch, HeadSHA, Status, Event, Workflow,
  Page, Limit. Status/Event 'all' treated as no-filter.

internal/tools/issue_list.go:
- Default state=open, default limit=30 (matches repo_list).
- next_page returned only when len(issues) == limit.

internal/tools/workflow_run_list.go:
- Default limit=10 (most common use is 'what just happened',
  not paging).
- Returns runs + total + optional next_page.

Tests: table-driven for both — happy path, empty result, filter
combinations, allowlist rejection. workflow_run_list also asserts
the 'status=all is no-op' behavior (no query param emitted).

Closes #28
Closes #29

cmd/gitea-mcp/main.go

@@ -66,8 +66,10 @@ func main() {
 	reg.Register(tools.NewRepoTree(giteaClient, ownerAllow))
 	reg.Register(tools.NewRepoTopicsUpdate(giteaClient, ownerAllow))
 	reg.Register(tools.NewIssueGet(giteaClient, ownerAllow))
+	reg.Register(tools.NewIssueList(giteaClient, ownerAllow))
 	reg.Register(tools.NewIssueClose(giteaClient, ownerAllow))
 	reg.Register(tools.NewIssueReopen(giteaClient, ownerAllow))
+	reg.Register(tools.NewWorkflowRunList(giteaClient, ownerAllow))
 	reg.Register(tools.NewReleaseCreate(giteaClient, ownerAllow))
 	reg.Register(tools.NewRepoDelete(giteaClient, ownerAllow))