feat: bulk validator tab + status/niche/type browse filters

- New app/validator.py: background HTTP checker for entire dataset
  - 50 concurrent checks, skips already-validated domains
  - Extracts prescreen_status, server, IP, load_time_ms
  - start/stop/status API at /api/validator/start|stop|status

- New dedicated "Validator 🔬" tab with stats grid, TLD filter,
  Start/Stop controls, live progress indicator

- Browse tab: "Live" column replaced with "Status" dot (color-coded
  ● from prescreen_status, falls back to is_live)
- Browse tab: new Status / Niche / Type filter dropdowns

- db.py: added ip TEXT + load_time_ms INTEGER columns + migrations;
  get_enriched() supports prescreen_status/niche/site_type filters

- main.py: /api/enriched extended with prescreen_status/niche/site_type

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

app/main.py

@@ -22,6 +22,7 @@ from app.db import (
 )
 from app.enricher import start_worker, pause_worker, resume_worker, is_running, ensure_workers_alive
 from app.scorer import run_scoring
+from app.validator import start_validator, stop_validator, get_validator_status
 
 logging.basicConfig(level=logging.INFO, format="%(asctime)s %(levelname)s %(message)s")
 logger = logging.getLogger(__name__)
@@ -158,17 +159,40 @@ async def enriched(
     kit_digital: Optional[bool] = Query(None),
     ai_only: bool = Query(False),
     lead_quality: str = Query(None),
+    prescreen_status: str = Query(None),
+    niche: str = Query(None),
+    site_type: str = Query(None),
     page: int = Query(1, ge=1),
     limit: int = Query(100, ge=1, le=1000),
 ):
     total, rows = await get_enriched(
         min_score=min_score, cms=cms, country=country,
         kit_digital=kit_digital, ai_only=ai_only, lead_quality=lead_quality,
+        prescreen_status=prescreen_status, niche=niche, site_type=site_type,
         page=page, limit=limit,
     )
     return {"page": page, "limit": limit, "total": total, "results": rows}
 
 
+# ── Bulk Validator endpoints ──────────────────────────────────────────────────
+
+@app.post("/api/validator/start")
+async def validator_start(tld: str = Query(None)):
+    start_validator(tld_filter=tld or None)
+    return get_validator_status()
+
+
+@app.post("/api/validator/stop")
+async def validator_stop():
+    stop_validator()
+    return {"status": "stopped"}
+
+
+@app.get("/api/validator/status")
+async def validator_status():
+    return get_validator_status()
+
+
 # ── AI assessment endpoints ───────────────────────────────────────────────────
 
 @app.post("/api/prescreen/batch")