feat(tasks): Add unified task-based worker architecture

Replace fragmented job systems (job_schedules, dispensary_crawl_jobs, SyncOrchestrator)
with a single unified task queue:

- Add worker_tasks table with atomic task claiming via SELECT FOR UPDATE SKIP LOCKED
- Add TaskService for CRUD, claiming, and capacity metrics
- Add TaskWorker with role-based handlers (resync, discovery, analytics)
- Add /api/tasks endpoints for management and migration from legacy systems
- Add TasksDashboard UI and integrate task counts into main dashboard
- Add comprehensive documentation

Task roles: store_discovery, entry_point_discovery, product_discovery, product_resync, analytics_refresh

Run workers with: WORKER_ROLE=product_resync npx tsx src/tasks/task-worker.ts

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

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

backend/src/tasks/handlers/store-discovery.ts

@@ -0,0 +1,67 @@
+/**
+ * Store Discovery Handler
+ *
+ * Discovers new stores on a platform (e.g., Dutchie) by crawling
+ * location APIs and adding them to dutchie_discovery_locations.
+ */
+
+import { TaskContext, TaskResult } from '../task-worker';
+import { DiscoveryCrawler } from '../../discovery/discovery-crawler';
+
+export async function handleStoreDiscovery(ctx: TaskContext): Promise<TaskResult> {
+  const { pool, task } = ctx;
+  const platform = task.platform || 'dutchie';
+
+  console.log(`[StoreDiscovery] Starting discovery for platform: ${platform}`);
+
+  try {
+    // Get states to discover
+    const statesResult = await pool.query(`
+      SELECT code FROM states WHERE active = true ORDER BY code
+    `);
+    const stateCodes = statesResult.rows.map(r => r.code);
+
+    if (stateCodes.length === 0) {
+      return { success: true, storesDiscovered: 0, message: 'No active states to discover' };
+    }
+
+    let totalDiscovered = 0;
+    let totalPromoted = 0;
+
+    // Run discovery for each state
+    const crawler = new DiscoveryCrawler(pool);
+
+    for (const stateCode of stateCodes) {
+      // Heartbeat before each state
+      await ctx.heartbeat();
+
+      console.log(`[StoreDiscovery] Discovering stores in ${stateCode}...`);
+
+      try {
+        const result = await crawler.discoverState(stateCode);
+        totalDiscovered += result.locationsDiscovered || 0;
+        totalPromoted += result.locationsPromoted || 0;
+        console.log(`[StoreDiscovery] ${stateCode}: discovered ${result.locationsDiscovered}, promoted ${result.locationsPromoted}`);
+      } catch (error: any) {
+        console.error(`[StoreDiscovery] Error discovering ${stateCode}:`, error.message);
+        // Continue with other states
+      }
+    }
+
+    console.log(`[StoreDiscovery] Complete: ${totalDiscovered} discovered, ${totalPromoted} promoted`);
+
+    return {
+      success: true,
+      storesDiscovered: totalDiscovered,
+      storesPromoted: totalPromoted,
+      statesProcessed: stateCodes.length,
+      newStoreIds: [], // Would be populated with actual new store IDs for chaining
+    };
+  } catch (error: any) {
+    console.error(`[StoreDiscovery] Error:`, error.message);
+    return {
+      success: false,
+      error: error.message,
+    };
+  }
+}