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/lifecycle/hostpool.go

@@ -8,6 +8,7 @@ import (
 	"time"
 
 	"git.omukk.dev/wrenn/sandbox/internal/db"
+	"git.omukk.dev/wrenn/sandbox/internal/id"
 	"git.omukk.dev/wrenn/sandbox/proto/hostagent/gen/hostagentv1connect"
 )
 
@@ -53,10 +54,10 @@ func (p *HostClientPool) Get(hostID, address string) hostagentv1connect.HostAgen
 // GetForHost is a convenience wrapper that extracts the address from a db.Host
 // and returns an error if the host has no address recorded yet.
 func (p *HostClientPool) GetForHost(h db.Host) (hostagentv1connect.HostAgentServiceClient, error) {
-	if !h.Address.Valid || h.Address.String == "" {
-		return nil, fmt.Errorf("host %s has no address", h.ID)
+	if h.Address == "" {
+		return nil, fmt.Errorf("host %s has no address", id.FormatHostID(h.ID))
 	}
-	return p.Get(h.ID, h.Address.String), nil
+	return p.Get(id.FormatHostID(h.ID), h.Address), nil
 }
 
 // Evict removes the cached client for the given host, forcing a new client to be