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)

src/lib/db/schema.ts

@@ -1,13 +1,22 @@
-import { sqliteTable, integer, real, text } from 'drizzle-orm/sqlite-core';
+import { sqliteTable, integer, real, text, uniqueIndex } from 'drizzle-orm/sqlite-core';
+
+export const charts = sqliteTable('charts', {
+  id: integer('id').primaryKey({ autoIncrement: true }),
+  name: text('name').notNull().unique(),
+  created_at: integer('created_at').notNull(),
+});
 
 export const candles = sqliteTable('candles', {
   id: integer('id').primaryKey({ autoIncrement: true }),
-  time: integer('time').notNull().unique(),
+  chart_id: integer('chart_id').notNull().references(() => charts.id),
+  time: integer('time').notNull(),
   open: real('open').notNull(),
   high: real('high').notNull(),
   low: real('low').notNull(),
   close: real('close').notNull(),
-});
+}, (table) => [
+  uniqueIndex('candles_chart_time_unique').on(table.chart_id, table.time),
+]);
 
 export const annotationTypes = sqliteTable('annotation_types', {
   id: integer('id').primaryKey({ autoIncrement: true }),
@@ -22,6 +31,7 @@ export const annotationTypes = sqliteTable('annotation_types', {
 
 export const annotations = sqliteTable('annotations', {
   id: integer('id').primaryKey({ autoIncrement: true }),
+  chart_id: integer('chart_id').notNull().references(() => charts.id),
   timestamp: integer('timestamp').notNull(),
   label_type: text('label_type').notNull(),
   geometry: text('geometry'), // JSON string for line coordinates