feat: add fileHash column to files schema

Update files database schema and test suite to support fileHash property.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/db/schema.ts

@@ -13,6 +13,7 @@ export const files = pgTable('files', {
   sizeBytes: bigint('size_bytes', { mode: 'number' }).notNull(),
   fileType: text('file_type').notNull(),
   uploaderId: bigint('uploader_id', { mode: 'number' }).notNull(),
+  fileHash: text('file_hash'),
   createdAt: timestamp('created_at').defaultNow().notNull(),
   updatedAt: timestamp('updated_at').defaultNow().notNull(),
 });

test/db.test.ts

@@ -25,6 +25,7 @@ describe('Database Layer', () => {
     expect(files.sizeBytes).toBeDefined();
     expect(files.fileType).toBeDefined();
     expect(files.uploaderId).toBeDefined();
+    expect(files.fileHash).toBeDefined();
     expect(files.createdAt).toBeDefined();
     expect(files.updatedAt).toBeDefined();
   });