Split API and frontend, migrate SQLite to PostgreSQL

- api.fahrschultermin.de: full API entry point with CORS + session auth
- fahrschultermin.de: frontend only, no more /api/v1 routing
- Database.php: PostgreSQL support (pgsql driver + lastval())
- All repositories: use Database::lastInsertId() for PG compatibility
- config/app.php: PostgreSQL connection settings + CORS config
- bootstrap.php: pass full $config to Database::configure()
- public/index.php: fetch-patch to redirect /api/v1 to api.fahrschultermin.de
- database/schema_pgsql.sql: full PostgreSQL schema (BIGSERIAL)
- database/import_pgsql.sql: 518 rows migrated from SQLite

www/fahrschultermin.de/app/Repositories/AppointmentRepository.php

@@ -84,7 +84,7 @@ final class AppointmentRepository extends BaseRepository
             'updated_at' => $timestamp,
         ]);
 
-        $appointmentId = (int) $this->db->lastInsertId();
+        $appointmentId = (int) $this->lastInsertId();
         $this->replaceUnits($appointmentId, $data['units_breakdown'] ?? []);
 
         return $this->find($tenantId, $appointmentId);

www/fahrschultermin.de/app/Repositories/BaseRepository.php

@@ -16,6 +16,11 @@ abstract class BaseRepository
         $this->db = Database::connection();
     }
 
+    protected function lastInsertId(): string
+    {
+        return Database::lastInsertId();
+    }
+
     protected function now(): string
     {
         return gmdate('c');

www/fahrschultermin.de/app/Repositories/InstructorRepository.php

@@ -45,7 +45,7 @@ final class InstructorRepository extends BaseRepository
             'updated_at' => $timestamp,
         ]);
 
-        return $this->find($tenantId, (int) $this->db->lastInsertId());
+        return $this->find($tenantId, (int) $this->lastInsertId());
     }
 
     public function update(int $tenantId, int $id, array $data): ?array

www/fahrschultermin.de/app/Repositories/ReferenceDataRepository.php

@@ -66,7 +66,7 @@ final class ReferenceDataRepository extends BaseRepository
             'created_at' => $timestamp,
             'updated_at' => $timestamp,
         ]);
-        $lessonTypeId = (int) $this->db->lastInsertId();
+        $lessonTypeId = (int) $this->lastInsertId();
         $this->replaceLessonTypeVisibility($tenantId, $lessonTypeId, $data['visible_template_ids'] ?? null);
 
         return $this->findLessonType($tenantId, $lessonTypeId);
@@ -225,7 +225,7 @@ final class ReferenceDataRepository extends BaseRepository
             'created_at' => $timestamp,
             'updated_at' => $timestamp,
         ]);
-        $templateId = (int) $this->db->lastInsertId();
+        $templateId = (int) $this->lastInsertId();
 
         $this->replaceTemplateRequirements($templateId, $data['requirements'] ?? []);
         $this->attachTemplateToExistingStudentLessonTypes($tenantId, $templateId);

www/fahrschultermin.de/app/Repositories/StudentRepository.php

@@ -60,7 +60,7 @@ final class StudentRepository extends BaseRepository
             'updated_at' => $timestamp,
         ]);
 
-        $studentId = (int) $this->db->lastInsertId();
+        $studentId = (int) $this->lastInsertId();
         $this->snapshotRequirements($studentId, (int) $data['template_id']);
 
         return $this->find($tenantId, $studentId);

www/fahrschultermin.de/app/Repositories/TenantRepository.php

@@ -40,7 +40,7 @@ final class TenantRepository extends BaseRepository
             'updated_at' => $timestamp,
         ]);
 
-        return $this->find((int) $this->db->lastInsertId());
+        return $this->find((int) $this->lastInsertId());
     }
 
     public function update(int $id, array $data): ?array

www/fahrschultermin.de/app/Repositories/UserRepository.php

@@ -74,7 +74,7 @@ final class UserRepository extends BaseRepository
             'updated_at' => $timestamp,
         ]);
 
-        return $this->findById((int) $this->db->lastInsertId());
+        return $this->findById((int) $this->lastInsertId());
     }
 
     public function update(int $id, array $data): ?array

www/fahrschultermin.de/app/Support/Database.php

@@ -5,15 +5,17 @@ declare(strict_types=1);
 namespace App\Support;
 
 use PDO;
+use PDOException;
 
 final class Database
 {
-    private static string $path;
     private static ?PDO $connection = null;
+    private static array $config = [];
 
-    public static function configure(string $path): void
+    public static function configure(array $config): void
     {
-        self::$path = $path;
+        self::$config = $config;
+        self::$connection = null; // reset on reconfigure
     }
 
     public static function connection(): PDO
@@ -22,16 +24,43 @@ final class Database
             return self::$connection;
         }
 
-        $directory = dirname(self::$path);
-        if (!is_dir($directory)) {
-            mkdir($directory, 0775, true);
+        $driver = self::$config['db_driver'] ?? 'sqlite';
+
+        if ($driver === 'pgsql') {
+            $host = self::$config['db_host'] ?? '127.0.0.1';
+            $port = self::$config['db_port'] ?? '5432';
+            $dbname = self::$config['db_database'] ?? '';
+            $user = self::$config['db_username'] ?? '';
+            $password = self::$config['db_password'] ?? '';
+
+            $dsn = "pgsql:host={$host};port={$port};dbname={$dbname}";
+            self::$connection = new PDO($dsn, $user, $password);
+        } else {
+            $path = self::$config['db_path'] ?? self::$config['db_path'] ?? '';
+            $directory = dirname($path);
+            if (!is_dir($directory)) {
+                mkdir($directory, 0775, true);
+            }
+            self::$connection = new PDO('sqlite:' . $path);
+            self::$connection->exec('PRAGMA foreign_keys = ON');
         }
 
-        self::$connection = new PDO('sqlite:' . self::$path);
         self::$connection->setAttribute(PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
         self::$connection->setAttribute(PDO::ATTR_DEFAULT_FETCH_MODE, PDO::FETCH_ASSOC);
-        self::$connection->exec('PRAGMA foreign_keys = ON');
 
         return self::$connection;
     }
+
+    public static function isPostgres(): bool
+    {
+        return (self::$config['db_driver'] ?? 'sqlite') === 'pgsql';
+    }
+
+    public static function lastInsertId(): string
+    {
+        if (self::isPostgres()) {
+            return self::$connection->query('SELECT lastval()')->fetchColumn();
+        }
+        return self::$connection->lastInsertId();
+    }
 }

www/fahrschultermin.de/app/bootstrap.php

@@ -36,7 +36,7 @@ if (!is_dir($sessionPath)) {
 session_save_path($sessionPath);
 session_start();
 
-Database::configure($config['db_path']);
+Database::configure($config);
 
 return [
     'config' => $config,