R7+ orchestrator + CC3 logo home: combined patches

Orchestrator-side:
- routers/img_proxy_router.py: 4xx/5xx → 1x1 transparent PNG (eliminates cascade <img onerror>)
- static/sport2.html: removed standalone three.min.js (3d-force-graph bundles), bumped to 1.73.4

CC3 (before limit hit):
- Logo home link applied to ALL HTML pages (admin.html, admin_users.html, audit.html, crm.html, erp.html, kpi.html, login.html)
- Backups in _backups/*.cc3_pre_logo.$ts

CC4 R3 (before plan mode):
- _backups/r3_cc4/ocr.py.pre_S2.$ts

Audit screenshots (80 pages) committed to _audit/audit_20260505_023639/shots/

static/admin_users.html

@@ -149,7 +149,7 @@ td.actions-col .btn { padding: 4px 8px; font-size: 11px; }
     <div class="brand">
       <div class="brand-mark">P</div>
       <div class="brand-text">
-        <h1>PGŽ SPORT</h1>
+        <h1><a href="/" style="text-decoration:none;color:inherit" title="Početna">PGŽ SPORT</a></h1>
         <div class="sub">Admin · Auth v3.0</div>
       </div>
     </div>