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/db/oauth.sql.go

@@ -7,6 +7,8 @@ package db
 
 import (
 	"context"
+
+	"github.com/jackc/pgx/v5/pgtype"
 )
 
 const getOAuthProvider = `-- name: GetOAuthProvider :one
@@ -38,10 +40,10 @@ VALUES ($1, $2, $3, $4)
 `
 
 type InsertOAuthProviderParams struct {
-	Provider   string `json:"provider"`
-	ProviderID string `json:"provider_id"`
-	UserID     string `json:"user_id"`
-	Email      string `json:"email"`
+	Provider   string      `json:"provider"`
+	ProviderID string      `json:"provider_id"`
+	UserID     pgtype.UUID `json:"user_id"`
+	Email      string      `json:"email"`
 }
 
 func (q *Queries) InsertOAuthProvider(ctx context.Context, arg InsertOAuthProviderParams) error {