feat: assessed filter, 5000 per-page limit, auto-advance on empty Not-checked page

Assessed/Not assessed filter:
- 'yes' → beauty_lead_quality IS NOT NULL (has been B2B assessed)
- 'no'  → beauty_lead_quality IS NULL (never assessed)
- wired through /api/enriched → get_enriched(beauty_assessed=)

Per-page limit:
- options: 100 / 500 / 1000 / 2000 / 5000
- backend cap raised from le=1000 to le=5000

Auto-advance on empty Not-checked page:
- after bulk validate/prescreen, loadDomains reloads the same DuckDB page
- if every domain on that page is now processed (client-side filter → 0 rows)
  but the page still returned results, automatically increment page and retry
- prevents "No domains found" after successfully processing a batch
- capped at page 500 to avoid infinite loop

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

app/db.py

@@ -337,6 +337,7 @@ async def get_enriched(min_score=0, cms=None, country=None, kit_digital=None,
                         prescreen_status=None, niche=None, site_type=None,
                         keyword=None, tld=None,
                         alpha_only=False, no_sld=False,
+                        beauty_assessed=None,
                         page=1, limit=100):
     offset = (page - 1) * limit
     conditions = ["score >= ?"]
@@ -379,6 +380,10 @@ async def get_enriched(min_score=0, cms=None, country=None, kit_digital=None,
         tld_clean = tld.lower().lstrip(".")
         conditions.append("LOWER(domain) LIKE ?")
         params.append(f"%.{tld_clean}")
+    if beauty_assessed == "yes":
+        conditions.append("beauty_lead_quality IS NOT NULL")
+    elif beauty_assessed == "no":
+        conditions.append("beauty_lead_quality IS NULL")
     if alpha_only:
         # No hyphens, no digits anywhere in the domain name
         conditions.append(