Switch database IDs from TEXT to native UUID

Consolidate 16 migrations into one with UUID columns for all entity
IDs. TEXT is kept only for polymorphic fields (audit_logs.actor_id,
resource_id) and template names. The id package now generates UUIDs
via google/uuid, with Format*/Parse* helpers for the prefixed wire
format (sb-{uuid}, usr-{uuid}, etc.). Auth context, services, and
handlers pass pgtype.UUID internally; conversion to/from prefixed
strings happens at API and RPC boundaries. Adds PlatformTeamID
(all-zeros UUID) for shared resources.

internal/sandbox/manager.go

@@ -96,7 +96,7 @@ func New(cfg Config) *Manager {
 // If sandboxID is empty, a new ID is generated.
 func (m *Manager) Create(ctx context.Context, sandboxID, template string, vcpus, memoryMB, timeoutSec int) (*models.Sandbox, error) {
 	if sandboxID == "" {
-		sandboxID = id.NewSandboxID()
+		sandboxID = id.FormatSandboxID(id.NewSandboxID())
 	}
 
 	if vcpus <= 0 {