feat: Support per-dispensary schedules (not just per-state)

- Add dispensary_id column to task_schedules table
- Update scheduler to handle single-dispensary schedules
- Update run-now endpoint to handle single-dispensary schedules
- Update frontend modal to pass dispensary_id when 1 store selected
- Fix existing "Deeply Rooted Hourly" schedule with dispensary_id=112

Now when you select ONE store and check "Make recurring", it creates
a schedule that runs for that specific store every interval.

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

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

backend/migrations/103_schedule_dispensary_id.sql

@@ -0,0 +1,12 @@
+-- Migration: 103_schedule_dispensary_id.sql
+-- Description: Add dispensary_id to task_schedules for per-store schedules
+-- Created: 2025-12-13
+
+-- Add dispensary_id column for single-store schedules
+ALTER TABLE task_schedules
+ADD COLUMN IF NOT EXISTS dispensary_id INTEGER REFERENCES dispensaries(id);
+
+-- Index for quick lookups
+CREATE INDEX IF NOT EXISTS idx_task_schedules_dispensary_id ON task_schedules(dispensary_id);
+
+COMMENT ON COLUMN task_schedules.dispensary_id IS 'For single-store schedules. If set, only this store is refreshed. If NULL, uses state_code for all stores in state.';