- C-3: inject setupLimiter into NewAdminAPI instead of package-level global
- H-5: generateRandomKey returns error instead of panicking
- H-6: replace init() bcrypt with sync.Once lazy initialization
- M-2: remove unsafe-inline from admin CSP script-src and style-src
- M-3: sanitize upload filenames (strip control chars, truncate to 255)
- M-5: truncate User-Agent to 512 bytes before storing as device
- M-10: MaxBodySizeUnless uses prefix matching instead of exact path
- M-12: wrap seedExistingDatabase in a single transaction
- M-13: use errors.Is for EOF check in upload handler
- M-14: log writeJSON encoding errors instead of discarding
- M-16: standardize error codes to INTERNAL_ERROR across all handlers