fix(templates): guard realpath crash in with-cloudflare-d1 on Cloudflare Workers

[SybyAbraham]

Problem

The with-cloudflare-d1 template crashes with a 500 on every request when deployed to Cloudflare Workers:

TypeError: Cannot read properties of undefined (reading 'endsWith')

The realpath() helper returns undefined when fs.existsSync() is false — which is the case for every process.argv entry in the Workers runtime (no filesystem). The subsequent .endsWith() call on undefined throws.

This was introduced in #15098, which replaced a simple regex check with realpath().endsWith() to also support payload run. The change works in Node.js but doesn't account for the Workers edge environment.

Fix

Two guards:

1. Try-catch around realpath() — fs.existsSync() and fs.realpathSync() may throw in runtimes without a filesystem.
2. Null check before .endsWith() — if realpath() returns undefined, return false instead of calling a method on undefined.

No behavioral change in Node.js — realpath() still returns the same values for existing file paths, and undefined for non-existent ones (which now safely returns false instead of throwing).

Verification

Deployed to Cloudflare Workers and confirmed:

• Homepage returns 200 (was 500)
• Admin panel loads and renders correctly
• Payload API endpoints respond normally
• No regressions in local dev (payload generate:types, payload migrate:create)