Normalize and propagate sandbox IDs
Add a normalizeId option to SandboxOptions and the Cloudflare provider.
When enabled, compute a lowercased normalizedId, pass it into the
CloudflareSandbox (id() now returns the normalized value), and persist
the normalized sandboxId to the DB when starting a sandbox. Also use
record.sandboxId as a fallback across API routes when interacting with
provider instances.