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/service/template.go

@@ -3,6 +3,8 @@ package service
 import (
 	"context"
 
+	"github.com/jackc/pgx/v5/pgtype"
+
 	"git.omukk.dev/wrenn/sandbox/internal/db"
 )
 
@@ -14,7 +16,7 @@ type TemplateService struct {
 
 // List returns all templates belonging to the given team. If typeFilter is
 // non-empty, only templates of that type ("base" or "snapshot") are returned.
-func (s *TemplateService) List(ctx context.Context, teamID, typeFilter string) ([]db.Template, error) {
+func (s *TemplateService) List(ctx context.Context, teamID pgtype.UUID, typeFilter string) ([]db.Template, error) {
 	if typeFilter != "" {
 		return s.DB.ListTemplatesByTeamAndType(ctx, db.ListTemplatesByTeamAndTypeParams{
 			TeamID: teamID,