Generate from embedded PGlite by default in the CLI

[qorud02]

Changes

db:generate now runs migrations in PGlite by default, so it can generate schema types and SQL without a PostgreSQL server. --no-pglite still selects the configured PostgreSQL database, and the direct generate() API keeps its existing default.

• Convert the config path to a file URL for dynamic import on Windows.
• Bind the embedded database gateway to 127.0.0.1.
• Document the CLI default and add a CLI regression test using an unreachable DATABASE_URL.

Verification

I ran the actual bundled CLI on Windows with Node. With the original configuration loader it failed with ERR_UNSUPPORTED_ESM_URL_SCHEME; with the loader fixed and the previous CLI default it tried the unreachable PostgreSQL address. The final default generated both the type file and SQL dump containing the migrated table. --no-pglite selected the external database as expected. All eight checks passed. Biome and git diff --check passed.

The Bun test runner was unavailable locally, so the new Bun regression test has not been run locally.

Fixes #2

@algora-pbc /claim #2