feat: add tags schema with Drizzle ORM integration

backend/src/database/schemas/tags.ts

@@ -0,0 +1,14 @@
+import { pgTable, varchar, timestamp, uuid, index } from 'drizzle-orm/pg-core';
+
+export const tags = pgTable('tags', {
+  id: uuid('id').primaryKey().defaultRandom(),
+  name: varchar('name', { length: 64 }).notNull().unique(),
+  slug: varchar('slug', { length: 64 }).notNull().unique(),
+  createdAt: timestamp('created_at', { withTimezone: true }).notNull().defaultNow(),
+  updatedAt: timestamp('updated_at', { withTimezone: true }).notNull().defaultNow(),
+}, (table) => ({
+  slugIdx: index('tags_slug_idx').on(table.slug),
+}));
+
+export type TagInDb = typeof tags.$inferSelect;
+export type NewTagInDb = typeof tags.$inferInsert;