Scraper: force-reset endpoint + watchdog to prevent stuck lock

Root cause: threading.Lock held indefinitely when Playwright browser
hangs inside run_in_executor (finally never fires from the async side).

Fixes:
- _acquire_scrape_lock/_release_scrape_lock track monotonic timestamp
- POST /competitors/scrape/reset force-releases the lock and marks any
  running batch as interrupted (queue rows stay intact for retry)
- GET /competitors/status now includes lock_held_seconds
- APScheduler watchdog job every 30 min auto-releases if held >3h
- Settings → Scraper Proxy tab shows live lock status (green/amber)
  with a Force Reset button requiring confirmation

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/pages/Settings.tsx

@@ -1,7 +1,7 @@
 import { useState, useEffect } from 'react'
 import { useParams, useNavigate } from 'react-router-dom'
 import { useQuery, useMutation, useQueryClient } from '@tanstack/react-query'
-import { Save, RefreshCw, Database, Clock, BedDouble, ChevronUp, ChevronDown, Network, ShieldCheck } from 'lucide-react'
+import { Save, RefreshCw, Database, Clock, BedDouble, ChevronUp, ChevronDown, Network, ShieldCheck, AlertTriangle } from 'lucide-react'
 import api from '../api'
 
 const TABS = [
@@ -488,6 +488,83 @@ function ProxyTab() {
           </div>
         </div>
       </div>
+
+      <ScraperLockCard />
+    </div>
+  )
+}
+
+// ─── Scraper Lock Status Card ─────────────────────────────────────────────────
+
+function ScraperLockCard() {
+  const qc = useQueryClient()
+
+  const { data: status, isLoading } = useQuery<{ lock_held_seconds: number | null }>({
+    queryKey: ['scraper-status-lock'],
+    queryFn: () => api.get('/competitors/status').then(r => r.data),
+    refetchInterval: 15000,
+  })
+
+  const resetM = useMutation({
+    mutationFn: () => api.post('/competitors/scrape/reset').then(r => r.data),
+    onSuccess: () => qc.invalidateQueries({ queryKey: ['scraper-status-lock'] }),
+  })
+
+  const held = status?.lock_held_seconds ?? null
+  const isStuck = held !== null && held > 0
+  const heldStr = held
+    ? held >= 3600
+      ? `${Math.floor(held / 3600)}h ${Math.floor((held % 3600) / 60)}m`
+      : held >= 60
+        ? `${Math.floor(held / 60)}m ${held % 60}s`
+        : `${held}s`
+    : null
+
+  return (
+    <div className="card" style={{ marginTop: 20 }}>
+      <div className="card-header">Scraper Lock</div>
+      <div style={{ padding: '16px 20px' }}>
+        <div style={{ display: 'flex', alignItems: 'center', gap: 12, marginBottom: 12 }}>
+          <span style={{
+            display: 'inline-flex', alignItems: 'center', gap: 6,
+            padding: '4px 10px', borderRadius: 20, fontSize: 13, fontWeight: 600,
+            background: isStuck ? '#fef3c7' : '#dcfce7',
+            color: isStuck ? '#d97706' : '#16a34a',
+          }}>
+            {isStuck
+              ? <><AlertTriangle size={13} strokeWidth={1.75} /> Locked ({heldStr})</>
+              : <><ShieldCheck size={13} strokeWidth={1.75} /> Idle</>}
+          </span>
+          {isStuck && (
+            <span style={{ fontSize: 12, color: 'var(--text-mid)' }}>
+              A scrape may be stuck. The watchdog will auto-release after 3 hours.
+            </span>
+          )}
+        </div>
+        <p style={{ fontSize: 13, color: 'var(--text-mid)', marginBottom: 12 }}>
+          Force-release the scrape lock if it is stuck (e.g. a hung Playwright browser).
+          Any in-progress scrape batch will be marked interrupted; the queue remains intact
+          and will retry on the next scheduled run or manual trigger.
+        </p>
+        <button
+          className="btn btn-sm"
+          style={{ background: '#fee2e2', color: '#dc2626', border: '1px solid #fca5a5' }}
+          disabled={resetM.isPending || isLoading}
+          onClick={() => {
+            if (window.confirm('Force-reset the scraper lock? Any running scrape will be interrupted.')) {
+              resetM.mutate()
+            }
+          }}
+        >
+          <RefreshCw size={13} strokeWidth={1.75} style={resetM.isPending ? { animation: 'spin 1.5s linear infinite' } : undefined} />
+          {resetM.isPending ? 'Resetting…' : 'Force Reset Lock'}
+        </button>
+        {resetM.isSuccess && (
+          <span style={{ marginLeft: 12, fontSize: 12, color: 'var(--success)' }}>
+            ✓ Reset — was {(resetM.data as any)?.was_locked ? 'locked' : 'already idle'}
+          </span>
+        )}
+      </div>
     </div>
   )
 }