feat: Add working hours for natural traffic patterns

Workers check their timezone (from preflight IP geolocation) and current
hour's weight probability to determine availability. This creates natural
traffic patterns - more workers active during peak hours, fewer during
off-peak. Tasks queue up at night and drain during the day.

Migrations:
- 099: working_hours table with hourly weights by profile
- 100: Add timezone column to worker_registry
- 101: Store timezone from preflight IP geolocation
- 102: check_working_hours() function with probability roll

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

backend/migrations/101_worker_preflight_timezone.sql

@@ -0,0 +1,78 @@
+-- Migration: 101_worker_preflight_timezone.sql
+-- Description: Update update_worker_preflight to extract timezone from fingerprint
+-- Created: 2024-12-13
+
+CREATE OR REPLACE FUNCTION public.update_worker_preflight(
+  p_worker_id character varying,
+  p_transport character varying,
+  p_status character varying,
+  p_ip character varying DEFAULT NULL,
+  p_response_ms integer DEFAULT NULL,
+  p_error text DEFAULT NULL,
+  p_fingerprint jsonb DEFAULT NULL
+)
+RETURNS void
+LANGUAGE plpgsql
+AS $function$
+DECLARE
+  v_curl_status VARCHAR(20);
+  v_http_status VARCHAR(20);
+  v_overall_status VARCHAR(20);
+  v_timezone VARCHAR(50);
+BEGIN
+  IF p_transport = 'curl' THEN
+    UPDATE worker_registry
+    SET
+      preflight_curl_status = p_status,
+      preflight_curl_at = NOW(),
+      preflight_curl_ms = p_response_ms,
+      preflight_curl_error = p_error,
+      curl_ip = p_ip,
+      updated_at = NOW()
+    WHERE worker_id = p_worker_id;
+
+  ELSIF p_transport = 'http' THEN
+    -- Extract timezone from fingerprint JSON if present
+    v_timezone := p_fingerprint->>'detectedTimezone';
+
+    UPDATE worker_registry
+    SET
+      preflight_http_status = p_status,
+      preflight_http_at = NOW(),
+      preflight_http_ms = p_response_ms,
+      preflight_http_error = p_error,
+      http_ip = p_ip,
+      fingerprint_data = COALESCE(p_fingerprint, fingerprint_data),
+      -- Save extracted timezone
+      timezone = COALESCE(v_timezone, timezone),
+      updated_at = NOW()
+    WHERE worker_id = p_worker_id;
+  END IF;
+
+  -- Update overall preflight status
+  SELECT preflight_curl_status, preflight_http_status
+  INTO v_curl_status, v_http_status
+  FROM worker_registry
+  WHERE worker_id = p_worker_id;
+
+  -- Compute overall status
+  IF v_curl_status = 'passed' AND v_http_status = 'passed' THEN
+    v_overall_status := 'passed';
+  ELSIF v_curl_status = 'passed' OR v_http_status = 'passed' THEN
+    v_overall_status := 'partial';
+  ELSIF v_curl_status = 'failed' OR v_http_status = 'failed' THEN
+    v_overall_status := 'failed';
+  ELSE
+    v_overall_status := 'pending';
+  END IF;
+
+  UPDATE worker_registry
+  SET
+    preflight_status = v_overall_status,
+    preflight_at = NOW()
+  WHERE worker_id = p_worker_id;
+END;
+$function$;
+
+COMMENT ON FUNCTION update_worker_preflight(varchar, varchar, varchar, varchar, integer, text, jsonb)
+  IS 'Updates worker preflight status and extracts timezone from fingerprint for working hours';