feat: add Supabase CLI scaffold and client SDK setup

Initializes the local Supabase project (supabase/config.toml) and adds
a thin src/lib/supabase.ts wrapper around @supabase/supabase-js that
reads connection details from Vite env vars, tested with a mocked
createClient.

src/lib/supabase.test.ts

@@ -0,0 +1,22 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest'
+
+const createClientMock = vi.fn(() => ({ type: 'mock-supabase-client' }))
+
+vi.mock('@supabase/supabase-js', () => ({ createClient: createClientMock }))
+
+describe('supabase client setup', () => {
+  beforeEach(() => {
+    vi.resetModules()
+    createClientMock.mockClear()
+  })
+
+  it('creates the client with the URL and anon key read from Vite env vars', async () => {
+    vi.stubEnv('VITE_SUPABASE_URL', 'https://test-project.supabase.co')
+    vi.stubEnv('VITE_SUPABASE_ANON_KEY', 'test-anon-key')
+
+    const { supabase } = await import('./supabase')
+
+    expect(createClientMock).toHaveBeenCalledWith('https://test-project.supabase.co', 'test-anon-key')
+    expect(supabase).toEqual({ type: 'mock-supabase-client' })
+  })
+})

src/lib/supabase.ts

@@ -0,0 +1,6 @@
+import { createClient } from '@supabase/supabase-js'
+
+export const supabase = createClient(
+  import.meta.env.VITE_SUPABASE_URL,
+  import.meta.env.VITE_SUPABASE_ANON_KEY,
+)