Phases 2-4: Requester support, batches, webhooks, scraper registry

Phase 2 - Requester & Batch Support:
- core/database.py: Added create_job params (requester_*, batch_*, priority, callback_*)
- core/database.py: Added batch methods (create_batch, get_batch, update_batch_progress, get_batches)
- core/database.py: Added update_job_callback for tracking webhook delivery
- api/routes/batches.py: New endpoints:
  - POST /api/scrape/google-reviews/batch (submit batch)
  - GET /api/batches (list batches)
  - GET /api/batches/{id} (batch detail)
  - DELETE /api/batches/{id} (cancel batch)
- api_server_production.py: Updated /api/scrape with requester, priority, callback fields
- api_server_production.py: New primary endpoint POST /api/scrape/google-reviews

Phase 3 - Webhooks:
- services/job_callback_service.py: New service with:
  - JobCallbackService: send_job_callback, send_batch_callback, retry_failed_callbacks
  - JobCallbackDispatcher: Background worker for callback monitoring
  - Payload formats per spec (job.completed, job.failed, batch.completed)
  - Exponential backoff for retries
  - Error classification for failure payloads

Phase 4 - Scraper Registry:
- scrapers/registry.py: Database-backed version routing:
  - get_scraper(): Version/variant/A/B routing
  - _get_weighted_scraper(): Traffic-weighted random selection
  - 60-second TTL cache for performance
  - register_scraper, deprecate_scraper, update_traffic_allocation
  - LegacyScraperRegistry preserved for backwards compatibility

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

services/__init__.py

@@ -0,0 +1,29 @@
+"""
+Services module for ReviewIQ platform.
+
+Contains service classes for webhook delivery, job callbacks, and other
+business logic.
+"""
+from services.webhook_service import (
+    WebhookManager,
+    WebhookDispatcher,
+    WebhookDeliveryError,
+    verify_webhook_signature
+)
+from services.job_callback_service import (
+    JobCallbackService,
+    JobCallbackDispatcher,
+    CallbackStatus
+)
+
+__all__ = [
+    # Webhook service
+    'WebhookManager',
+    'WebhookDispatcher',
+    'WebhookDeliveryError',
+    'verify_webhook_signature',
+    # Job callback service
+    'JobCallbackService',
+    'JobCallbackDispatcher',
+    'CallbackStatus',
+]