fix: Turso/libsql HTTP adapter für Windows-Kompatibilität

- PrismaLibSql Factory statt pre-created client (URL_INVALID fix)
- libsql:// URL zu https:// konvertieren für @libsql/client/http
- prisma.config.ts nutzt TURSO_DATABASE_URL wenn gesetzt
- .env.local.example mit Turso-Docs erweitert
- @libsql/client auf 0.17.0 pinned

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/db.ts

@@ -1,8 +1,16 @@
 import { PrismaClient } from "@prisma/client";
 import { PrismaBetterSqlite3 } from "@prisma/adapter-better-sqlite3";
+import { PrismaLibSql } from "@prisma/adapter-libsql";
 
 // Prisma 7 requires a driver adapter for SQLite connections.
+// Uses Turso (cloud SQLite) when TURSO_DATABASE_URL is set, otherwise local file.
 function createPrisma() {
+  if (process.env.TURSO_DATABASE_URL) {
+    const url = process.env.TURSO_DATABASE_URL.replace(/^libsql:\/\//, "https://");
+    const adapter = new PrismaLibSql({ url, authToken: process.env.TURSO_AUTH_TOKEN });
+    return new PrismaClient({ adapter } as ConstructorParameters<typeof PrismaClient>[0]);
+  }
+
   const url = process.env.DATABASE_URL || "file:./leadflow.db";
   const adapter = new PrismaBetterSqlite3({ url });
   return new PrismaClient({ adapter } as ConstructorParameters<typeof PrismaClient>[0]);