fix: use standard @prisma/client imports instead of custom output path

The custom generator output to src/generated/prisma caused persistent
Turbopack module resolution failures in CI. Switch to the standard
@prisma/client import path which all bundlers resolve correctly.

- Remove custom output from prisma schema generator
- Update all imports from ../generated/prisma to @prisma/client
- Add postinstall script to auto-run prisma generate after npm ci
- Remove generated files from git (no longer needed in source tree)
- Simplify CI workflow (remove verify step and --webpack workaround)

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

src/data/filament.queries.ts

@@ -1,5 +1,5 @@
 import { prisma } from "@/lib/prisma";
-import { Prisma } from "../generated/prisma";
+import { Prisma } from "@prisma/client";
 import type { DataTableSearchParams } from "@/types/table.types";
 
 interface FilamentSearchParams extends DataTableSearchParams {