feat: two-phase pre-screening with HTTP check + DeepSeek batch classification

Phase 1 (no AI credits): httpx checks every selected domain concurrently
(30 parallel) with real browser UA — detects live/dead/parked/redirect.
Parked: keyword scan in body/title + known parking host redirect check.
Results saved to DB immediately; dead/parked never reach DeepSeek.

Phase 2 (single DeepSeek call): all live-site titles + snippets bundled
into ONE Replicate/DeepSeek-R1 request → returns niche + type for every
domain in batch (up to 80 per call, parallelised if more).

- app/prescreener.py (new): _check_one(), prescreen_domains(),
  classify_with_deepseek(), parking signal lists, same-domain redirect logic
- app/db.py: prescreen_status/niche/site_type/prescreen_at columns +
  migrations; save_prescreen_results() upsert helper
- app/main.py: POST /api/prescreen/batch endpoint
- app/static/index.html:
  - 🔍 Pre-screen button (disabled while running, shows spinner)
  - Niche + Type columns in Browse and Leads tables (.pni/.pty pills)
  - Prescreen status colour dot (●) when niche not yet set
  - prescreening state flag; result toast shows per-status counts

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

app/db.py

@@ -36,7 +36,11 @@ CREATE TABLE IF NOT EXISTS enriched_domains (
     ai_contact_channel TEXT,
     ai_contact_value TEXT,
     ai_assessed_at TEXT,
-    site_analysis TEXT
+    site_analysis TEXT,
+    prescreen_status TEXT,
+    niche TEXT,
+    site_type TEXT,
+    prescreen_at TEXT
 );
 CREATE TABLE IF NOT EXISTS job_queue (
     id INTEGER PRIMARY KEY AUTOINCREMENT,
@@ -76,6 +80,10 @@ _MIGRATIONS = [
     "ALTER TABLE enriched_domains ADD COLUMN site_analysis TEXT",
     "CREATE TABLE IF NOT EXISTS ai_queue (domain TEXT PRIMARY KEY, status TEXT DEFAULT 'pending', created_at TEXT DEFAULT (datetime('now')), completed_at TEXT, error TEXT)",
     "ALTER TABLE ai_queue ADD COLUMN language TEXT DEFAULT 'ES'",
+    "ALTER TABLE enriched_domains ADD COLUMN prescreen_status TEXT",
+    "ALTER TABLE enriched_domains ADD COLUMN niche TEXT",
+    "ALTER TABLE enriched_domains ADD COLUMN site_type TEXT",
+    "ALTER TABLE enriched_domains ADD COLUMN prescreen_at TEXT",
 ]
 
 # Index build state
@@ -418,6 +426,35 @@ async def save_ai_assessment(domain: str, assessment: dict, site_analysis: dict
         await db.commit()
 
 
+async def save_prescreen_results(results: list[dict]):
+    """Upsert prescreen HTTP results and/or DeepSeek niche/type classifications."""
+    async with aiosqlite.connect(SQLITE_PATH) as db:
+        for r in results:
+            domain = r.get("domain")
+            if not domain:
+                continue
+            niche     = r.get("niche")
+            site_type = r.get("type")   # DeepSeek returns "type" key
+            if niche or site_type:
+                # Classification-only update (domain row must already exist)
+                await db.execute(
+                    "UPDATE enriched_domains SET niche=?, site_type=? WHERE domain=?",
+                    (niche, site_type, domain),
+                )
+            else:
+                # Prescreen status upsert — create row if it doesn't exist yet
+                await db.execute(
+                    """INSERT INTO enriched_domains (domain, prescreen_status, prescreen_at, page_title)
+                       VALUES (?, ?, datetime('now'), ?)
+                       ON CONFLICT(domain) DO UPDATE SET
+                         prescreen_status = excluded.prescreen_status,
+                         prescreen_at     = excluded.prescreen_at,
+                         page_title       = COALESCE(page_title, excluded.page_title)""",
+                    (domain, r.get("prescreen_status"), r.get("title")),
+                )
+        await db.commit()
+
+
 async def queue_domains(domains: list[str]):
     async with aiosqlite.connect(SQLITE_PATH) as db:
         await db.executemany(