feat: add charts table schema and migration with data backfill

- Add charts table with id, name (unique), created_at
- Add chart_id FK to candles table with composite unique on (chart_id, time)
- Add chart_id FK to annotations table
- Custom migration handles existing data: creates 'Imported Data' chart and backfills chart_id
- Recreates tables for NOT NULL constraint (SQLite limitation)

drizzle/meta/_journal.json

@@ -15,6 +15,13 @@
       "when": 1770915891699,
       "tag": "0001_sticky_shinko_yamashiro",
       "breakpoints": true
+    },
+    {
+      "idx": 2,
+      "version": "6",
+      "when": 1770937855462,
+      "tag": "0002_careful_synch",
+      "breakpoints": true
     }
   ]
 }