SEC-API-2: WorkspaceGuard now propagates database errors as 500s instead of
returning "access denied". Only Prisma P2025 (record not found) is treated
as "user not a member".
SEC-API-3: PermissionGuard now propagates database errors as 500s instead of
returning null role (which caused permission denied). Only Prisma P2025 is
treated as "not a member".
This prevents connection timeouts, pool exhaustion, and other infrastructure
errors from being misreported to users as authorization failures.
Refs #337
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>