feat: Add Real-Time Inventory Tracking infrastructure

Implements per-store high-frequency crawl scheduling and inventory
snapshot tracking for sales velocity estimation (Hoodie Analytics parity).

Database migrations:
- 117: Per-store crawl_interval_minutes and next_crawl_at columns
- 118: inventory_snapshots table (30-day retention)
- 119: product_visibility_events table for OOS/brand alerts (90-day)

Backend changes:
- inventory-snapshots.ts: Shared utility normalizing Dutchie/Jane/Treez
- visibility-events.ts: Detects OOS, price changes, brand drops
- task-scheduler.ts: checkHighFrequencyStores() runs every 60s
- Handler updates: 2-line additions to save snapshots/events

API endpoints:
- GET /api/tasks/schedules/high-frequency
- PUT /api/tasks/schedules/high-frequency/:id
- DELETE /api/tasks/schedules/high-frequency/:id

Frontend:
- TasksDashboard: Per-Store Schedules section with stats

Features:
- Per-store intervals (15/30/60 min configurable)
- Jitter (0-20%) to avoid detection patterns
- Cross-platform support (Dutchie, Jane, Treez)
- No crawler core changes - scheduling/post-crawl only

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

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

backend/migrations/118_inventory_snapshots.sql

@@ -0,0 +1,48 @@
+-- Migration 118: Inventory snapshots table
+-- Lightweight per-product tracking for sales velocity estimation
+-- Part of Real-Time Inventory Tracking feature
+
+CREATE TABLE IF NOT EXISTS inventory_snapshots (
+  id BIGSERIAL PRIMARY KEY,
+  dispensary_id INT NOT NULL REFERENCES dispensaries(id) ON DELETE CASCADE,
+  product_id TEXT NOT NULL,           -- provider_product_id (normalized across platforms)
+  captured_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
+
+  -- Platform (for debugging/filtering)
+  platform TEXT NOT NULL,             -- 'dutchie' | 'jane' | 'treez'
+
+  -- Inventory fields (normalized from all platforms)
+  quantity_available INT,             -- Dutchie: quantityAvailable, Jane: quantity, Treez: quantityAvailable
+  is_below_threshold BOOLEAN,         -- Dutchie: isBelowThreshold, Jane: computed, Treez: lowInventory
+  status TEXT,                        -- Active/Inactive/available
+
+  -- Price fields (normalized)
+  price_rec NUMERIC(10,2),            -- recreational price
+  price_med NUMERIC(10,2),            -- medical price (if different)
+
+  -- Denormalized for fast queries
+  brand_name TEXT,
+  category TEXT,
+  product_name TEXT
+);
+
+-- Primary query: get snapshots for a store over time
+CREATE INDEX idx_inv_snap_store_time ON inventory_snapshots(dispensary_id, captured_at DESC);
+
+-- Delta calculation: get consecutive snapshots for a product
+CREATE INDEX idx_inv_snap_product_time ON inventory_snapshots(dispensary_id, product_id, captured_at DESC);
+
+-- Brand-level analytics
+CREATE INDEX idx_inv_snap_brand_time ON inventory_snapshots(brand_name, captured_at DESC) WHERE brand_name IS NOT NULL;
+
+-- Platform filtering
+CREATE INDEX idx_inv_snap_platform ON inventory_snapshots(platform, captured_at DESC);
+
+-- Retention cleanup (30 days)
+CREATE INDEX idx_inv_snap_cleanup ON inventory_snapshots(captured_at) WHERE captured_at < NOW() - INTERVAL '30 days';
+
+-- Comments
+COMMENT ON TABLE inventory_snapshots IS 'Lightweight inventory snapshots for sales velocity tracking. Retained 30 days.';
+COMMENT ON COLUMN inventory_snapshots.product_id IS 'Provider product ID, normalized across platforms';
+COMMENT ON COLUMN inventory_snapshots.platform IS 'Menu platform: dutchie, jane, or treez';
+COMMENT ON COLUMN inventory_snapshots.quantity_available IS 'Current quantity in stock (Dutchie: quantityAvailable, Jane: quantity)';