fix(ci): correct swagger path + add deploy concurrency guard

Iteration 2 fix: /api/swagger → /swagger (correct ASP.NET default).

Iteration 3 — Concurrency guard:
- concurrency group 'deploy-production': ensures only one deploy
  runs at a time (cancel-in-progress: false so queued deploys
  wait instead of being cancelled).
- Why: prevents race conditions when CI-triggered workflow_run
  and manual workflow_dispatch overlap. Without this, parallel
  deploys could corrupt docker compose state or conflict on
  shared resources (ports, volumes, version tags).

.gitea/workflows/deploy.yaml

@@ -1,6 +1,13 @@
 name: Deploy to Production
 run-name: 🚀 Deploy ${{ inputs.bump_version || 'patch' }} by @${{ gitea.actor }}
 
+# ── Concurrency: one deploy at a time, cancel queued ones ──
+# Why: prevents race conditions when CI triggers deploy while
+#   a manual deploy is still running. The latest deploy wins.
+concurrency:
+  group: deploy-production
+  cancel-in-progress: false
+
 # ───────────────────────────────────────────────────
 # Trigger: automatic after CI success, or manual dispatch.
 # Runner: uses ubuntu-latest label (consistently present on
@@ -205,7 +212,7 @@ jobs:
 
           check "/dashboard" "Dashboard"    200
           check "/health"    "Health API"   200
-          check "/api/swagger" "API Swagger" 200
+          check "/swagger"   "API Swagger"  200
 
           echo ""
           echo "Results: $PASS passed, $FAIL failed"