fix: skip local runtime checks for gen types --db-url

[surajshekhar]

What kind of change does this PR introduce?

Bug fix.

What is the current behavior?

supabase gen types --db-url ... still attempts to load local Supabase runtime/profile state and fails with:

supabase start is not running

even when a direct PostgreSQL connection URL is explicitly provided.

Fixes #5283

What is the new behavior?

When --db-url is explicitly provided, the CLI now bypasses local runtime validation and directly uses the supplied PostgreSQL connection.

This prevents unnecessary:

• local profile loading
• local runtime checks
• dependency on supabase start

Additional context

The fix adds explicit detection for --db-url usage in the command flow and skips local runtime validation in the legacy Go type generation path.

Added targeted regression coverage for the --db-url bypass behavior in internal/gen/types/types_test.go.