feat: add duplicate email detection via auth hook with fallback

- Add before-user-created hook function for server-side duplicate email detection
- Implement fallback detection using identities array check (Supabase limitation)
- Update signUpWithPassword to detect duplicate emails via hook errors or empty identities
- Add error handling in login page to show duplicate email errors and auto-switch to login mode
- Add auth hook setup documentation and test scripts
- Add password reset and update password flows
- Add email templates for signup confirmation and password reset

scripts/apply-migration.ts

@@ -0,0 +1,71 @@
+#!/usr/bin/env tsx
+/**
+ * Apply Migration Script
+ * Executes a SQL migration file directly against the Supabase database
+ */
+
+import { createClient } from '@supabase/supabase-js'
+import { readFileSync } from 'fs'
+import { join } from 'path'
+
+const supabaseUrl = process.env.NEXT_PUBLIC_SUPABASE_URL!
+const supabaseServiceKey = process.env.SUPABASE_SERVICE_ROLE_KEY!
+
+if (!supabaseUrl || !supabaseServiceKey) {
+  console.error('❌ Missing Supabase credentials')
+  console.error('   Make sure NEXT_PUBLIC_SUPABASE_URL and SUPABASE_SERVICE_ROLE_KEY are set')
+  process.exit(1)
+}
+
+const supabase = createClient(supabaseUrl, supabaseServiceKey, {
+  auth: {
+    autoRefreshToken: false,
+    persistSession: false
+  }
+})
+
+async function applyMigration(migrationFile: string) {
+  console.log(`🔄 Applying migration: ${migrationFile}\n`)
+
+  try {
+    // Read migration file
+    const migrationPath = join(process.cwd(), 'supabase/migrations', migrationFile)
+    const sql = readFileSync(migrationPath, 'utf-8')
+
+    // Execute SQL
+    const { data, error } = await supabase.rpc('exec_sql', { sql_query: sql })
+
+    if (error) {
+      // Try alternative approach - direct query
+      const statements = sql
+        .split(';')
+        .map(s => s.trim())
+        .filter(s => s.length > 0 && !s.startsWith('--'))
+
+      for (const statement of statements) {
+        const { error: stmtError } = await supabase.rpc(statement)
+        if (stmtError) {
+          console.error('❌ Error executing statement:', stmtError.message)
+          throw stmtError
+        }
+      }
+    }
+
+    console.log('✅ Migration applied successfully!')
+    console.log('\n📝 Next steps:')
+    console.log('   1. Run: pnpm run setup:auth-hook')
+    console.log('   2. Configure hook link in Supabase Dashboard')
+
+  } catch (error: any) {
+    console.error('❌ Migration failed:', error.message)
+    console.log('\n💡 Alternative: Apply manually via Supabase Dashboard')
+    console.log('   1. Go to: https://supabase.com/dashboard/project/_/sql')
+    console.log('   2. Copy contents of:', migrationFile)
+    console.log('   3. Paste and run in SQL Editor')
+    process.exit(1)
+  }
+}
+
+// Get migration file from command line or use latest
+const migrationFile = process.argv[2] || '20251119094908_auth_hook_duplicate_email.sql'
+applyMigration(migrationFile)