feat(gitea): surface mathias's own open Gitea issues on stage 03 (#4)

TDD: IssueNodes parses /repos/issues/search into stage nodes (title, repo
tag, clickable html_url). gitea.MyIssues() reads GITEA_TOKEN and skips
gracefully when unset, mirroring the existing liveOverlay fallback pattern.

Single-operator homelab, not per-visitor OAuth: a static read-only PAT
gates on "cleared Authentik forward-auth", not per-user token exchange —
see #4 discussion. GITEA_TOKEN provisioning in infra (ExternalSecret) is
a separate follow-up; without it the overlay is inert (no crash, just no
live nodes), so this ships safely ahead of that wiring.

Nodes with a url now render as clickable <a class="node"> instead of
<div class="node">.

internal/atlas/issues.go

@@ -0,0 +1,32 @@
+package atlas
+
+import (
+	"encoding/json"
+	"fmt"
+)
+
+// IssueNodes parses a Gitea `/repos/issues/search` response (the
+// authenticated user's own open issues, newest first) into one node per
+// issue, linking out to the issue.
+func IssueNodes(searchJSON []byte) ([]Node, error) {
+	var issues []struct {
+		Number     int    `json:"number"`
+		Title      string `json:"title"`
+		HTMLURL    string `json:"html_url"`
+		Repository struct {
+			FullName string `json:"full_name"`
+		} `json:"repository"`
+	}
+	if err := json.Unmarshal(searchJSON, &issues); err != nil {
+		return nil, fmt.Errorf("parse issues: %w", err)
+	}
+	nodes := make([]Node, 0, len(issues))
+	for _, i := range issues {
+		nodes = append(nodes, Node{
+			Title: fmt.Sprintf("#%d %s", i.Number, i.Title),
+			Tags:  []string{"live · Gitea", i.Repository.FullName},
+			URL:   i.HTMLURL,
+		})
+	}
+	return nodes, nil
+}