Add schema support

[atilafassina]

This PR adds support to SQL seed scripts

---

To test it

1. pull this branch, go to /examples/tanstack-start
2. observe schema.sql on root of this app, adjust the schema to your needs
3. run the dev server

Easiest way to confirm the schema and data have been pushed is to claim the newly created DB to your account and check on Neon's Console.

[guillaumervls]

Besides comments in the code:

• it's probably simpler that instantNeon accepts ~ the same argument structure as the vite plugin.
• less terms/names is better, so I'd go either for "seed" or "onCreate". Probably seed is actually better than "onCreate", so the onCreate would be better named seed.

[guillaumervls]

I see you removed schema.json, probably those lines can be simplified in the release workflow file https://github.com/neondatabase/neondb-cli/blob/c1bf20c61bd64f35a071f74e95efadca56dd2765/.github/workflows/release.yml#L80-L94

[guillaumervls]

(we're getting there! 🙌 )

[Copilot]

Pull Request Overview

This PR adds support for seeding a SQL script during database initialization. Key changes include:

• Modifying the InstantNeon API and postgresPlugin to accept a new seed option.
• Introducing a new CLI flag to specify a SQL file for seeding.
• Updating documentation, examples, and changelogs accordingly.

Reviewed Changes

Copilot reviewed 23 out of 24 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
packages/vite-plugin-postgres/src/index.ts	Updated options to use InstantNeonParams and forward the seed option.
packages/vite-plugin-postgres/README.md	Documented the new seed option and provided usage examples.
packages/neondb/src/lib/utils/args.ts	Added new CLI flag (sql) for specifying the seed file; updates to help text.
packages/neondb/src/lib/types.ts	Added the SqlScript type and updated InstantNeonParams with seed support.
packages/neondb/src/lib/seed-database.ts	Introduced a function to execute SQL seed commands after DB creation.
packages/neondb/src/lib/instant-neon.ts	Integrated seed support to push the schema if provided.
packages/neondb/src/cli.ts	Modified CLI logic to prompt/handle the seed file flag and pass through.
Other files (package.json, examples, changsets)	Updated scripts, examples, and changelogs for the new schema seeding feature.

Comments suppressed due to low confidence (1)

packages/neondb/src/lib/utils/args.ts:26

• The CLI flag for specifying the SQL seed file is defined as 'sql' here, but the documentation and examples reference '--seed'. Consider aligning the flag name across the code and documentation for consistency.

			sql: {