Add MODE=pcb layout exam job with AI and deterministic checks.

Parallel pcb_status pipeline: parse board, classify domains/groups,
inventory traces, PE-LAY/PLC/SI/DRT checks, per-IC datasheet review.
Findings merge into the report UI. No auto-place or pcbnew write-back.

backend/routers/projects.py

@@ -148,6 +148,9 @@ async def get_project(project_id: str, request: Request):
     healed_pl = proj_svc.heal_if_placement_stuck(storage, owner_user_id, project_id)
     if healed_pl is not None:
         meta = healed_pl
+    healed_pcb = proj_svc.heal_if_pcb_stuck(storage, owner_user_id, project_id)
+    if healed_pcb is not None:
+        meta = healed_pcb
     return meta.model_dump()