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/web/static/cad-atlas.html

@@ -111,8 +111,8 @@
   .stage .no{color:var(--dim);font-size:11px;letter-spacing:2px}
   .stage h2{font-size:17px;margin:6px 0 2px}
   .stage .path{color:var(--mono);font-size:11.5px;margin-bottom:6px;min-height:16px}
-  .node{border:1px solid var(--line);border-radius:11px;background:var(--panel);
-    padding:12px 13px;margin-top:12px;position:relative;
+  .node{display:block;border:1px solid var(--line);border-radius:11px;background:var(--panel);
+    padding:12px 13px;margin-top:12px;position:relative;color:inherit;text-decoration:none;
     transition:border-color .25s,box-shadow .25s,transform .25s}
   .node .t{font-weight:600;margin-bottom:3px;display:flex;align-items:center;gap:7px}
   .node .d{color:var(--dim);font-size:12px}
@@ -246,7 +246,9 @@ function renderAtlas(){
       if(n.risk)inner+=`<div class="risk mono"><span class="lo">LOW · auto</span><span class="md">MED · ntfy gate</span><span class="hi">HIGH · blocked</span></div>`;
     }
     if(n.gate)inner+=`<div class="gatebtns mono"><div class="g ok">✓ approve</div><div class="g no">✕ reject</div></div>`;
-    h+=`<div class="node ${n.cls||''}">${inner}</div>`;
+    const tag = n.url ? 'a' : 'div';
+    const link = n.url ? ` href="${n.url}" target="_blank" rel="noopener"` : '';
+    h+=`<${tag} class="node ${n.cls||''}"${link}>${inner}</${tag}>`;
   });
   st.innerHTML=h;track.appendChild(st);stageEls.push(st);
   // stacked-layout transition row (shown on mobile where the SVG spine is hidden)