imaging dashboard: add Clear all button + endpoint

New /imaging/delete_all endpoint wipes every per-bay JSON in IMAGING_DIR
via imaging_status.delete_all_sessions(). Template adds "Clear all"
outline-danger button next to the count badge, gated on sessions list
non-empty, with confirm() prompt naming the count.

Deployed via scp + systemctl restart pxe-webapp on 172.16.9.1.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

webapp/app.py

@@ -496,6 +496,14 @@ def imaging_delete_session(serial):
     return redirect(url_for("imaging_dashboard"))
 
 
+@app.route("/imaging/delete_all", methods=["POST"])
+def imaging_delete_all():
+    n = imaging_status.delete_all_sessions()
+    audit("IMAGING_DELETE_ALL", str(n))
+    flash(f"Cleared {n} imaging session(s).", "success")
+    return redirect(url_for("imaging_dashboard"))
+
+
 @app.route("/imaging/<serial>/laps", methods=["POST"])
 def imaging_set_laps(serial):
     """Save (or clear with empty value) the LAPS password for a bay so it

webapp/services/imaging_status.py

@@ -169,3 +169,18 @@ def delete_session(serial: str) -> bool:
         return True
     except OSError:
         return False
+
+
+def delete_all_sessions() -> int:
+    """Wipe every per-bay JSON in IMAGING_DIR. Returns count removed."""
+    _ensure_dir()
+    removed = 0
+    for fn in os.listdir(config.IMAGING_DIR):
+        if not fn.endswith(".json"):
+            continue
+        try:
+            os.unlink(os.path.join(config.IMAGING_DIR, fn))
+            removed += 1
+        except OSError:
+            pass
+    return removed

webapp/templates/imaging.html

@@ -23,7 +23,16 @@ window.addEventListener('DOMContentLoaded', scheduleImagingReload);
     <h2 class="mb-0">Imaging Progress</h2>
     <small class="text-muted">Auto-refresh 15s. POST updates from imaging clients arrive at <code>/imaging/status</code>.</small>
   </div>
+  <div class="d-flex align-items-center gap-2">
     <span class="badge bg-secondary fs-6"><span id="visible-count">{{ sessions|length }}</span>/{{ sessions|length }}</span>
+    {% if sessions %}
+    <form method="post" action="{{ url_for('imaging_delete_all') }}"
+          onsubmit="return confirm('Clear all {{ sessions|length }} imaging session(s)? This wipes every tile from the dashboard. Live re-images will repopulate on next status push.');"
+          style="display:inline;">
+      <button type="submit" class="btn btn-sm btn-outline-danger">Clear all</button>
+    </form>
+    {% endif %}
+  </div>
 </div>
 
 <div class="mb-3">