fix(db): schema types with rolldown rc

[onmax]

Fixes #821

Problem

• With Vite 8 + rolldown rc.* overrides, DB schema type generation during nuxt prepare can fail.
• I saw two failure modes:
  • rolldown validation warning about an unsupported debug input option (coming from tsdown/rolldown API drift)
  • fatal [TSCONFIG_ERROR] ... Tsconfig not found when schema types are emitted from .nuxt/hub/db/schema.entry.ts in some environments

What Changed

• Bump tsdown dependency to ^0.20.3.
• Generate .nuxt/hub/db/tsconfig.json (template) for schema type generation.
• Pass that tsconfig to buildDatabaseSchema() and sanitize rolldown input options (debug).
• Auto-create tsconfig fallback in buildDatabaseSchema() for direct callers (CLI, tests) where Nuxt templates haven't been written.
• Add inlineOnly: false to suppress tsdown 0.20.3 dependency detection warning with skipNodeModulesBundle: false.

StackBlitz

	Link	Expected
Bug	hub-821	Warnings/errors
Fix	hub-821-fix	Clean prepare

[vercel]

@onmax is attempting to deploy a commit to the NuxtLabs Team on Vercel.

A member of the Team first needs to authorize it.

[atinux]

Happy to resolve the conflicts @onmax ?

[onmax]

CI test failures are a pre-existing Nuxt 4.3.1 issue (Cannot find module '#build/route-rules.mjs') — same failure on main's latest commit. Tracked in nuxt/nuxt#34164

Lint passes. Our changes are clean.

[onmax]

for context, I made a repro for Cannot find module '#build/route-rules.mjs'.

nuxt/nuxt#34392 (comment)