fix: resolve frontend-to-backend mapping gaps across API types, config fields, and issuer IDs

Full audit of all ~100 backend API endpoints against frontend client functions
and TypeScript interfaces. Fixes field name mismatches, missing client functions,
phantom interface fields, type coercion for Go bool/int config fields, and
issuer type ID alignment with backend domain constants.

Backend:
- issuer.go/target.go: GUI-created entities default enabled=true (Go bool
  zero value was overriding DB DEFAULT)

Frontend types (types.ts):
- Certificate: fingerprint→fingerprint_sha256, phantom fields made optional
- CertificateVersion: fingerprint→fingerprint_sha256, chain_pem→pem_chain,
  removed phantom version/cert_pem fields
- Job: error_message→last_error (matches Go json tag)

Frontend client (client.ts):
- Added getNotification(id) and getAuditEvent(id) for existing backend routes

Frontend pages:
- CertificateDetailPage: derives serial/fingerprint/issuedAt from latest
  CertificateVersion instead of empty Certificate fields
- JobsPage/JobDetailPage: error_message→last_error
- TargetsPage: reload_cmd→reload_command, validate_cmd→validate_command,
  added missing config fields per backend structs (validate_command for
  NGINX/Apache, hostname/winrm_timeout for IIS, private_key/passphrase/
  cert_mode/key_mode for SSH, winrm_https/winrm_insecure for WinCertStore,
  create_keystore for JavaKeystore, mode for Dovecot), type coercion via
  buildConfigPayload() with BOOL_FIELDS/INT_FIELDS sets, IIS WinRM nesting
- TargetDetailPage: added passphrase to sensitiveKeys redaction
- issuerTypes.ts: type IDs aligned to backend constants (acme→ACME,
  local→GenericCA, stepca→StepCA, openssl→OpenSSL), backward compat aliases
  preserved, step-ca config fields updated to match backend struct

Utilities (utils.ts):
- formatDate/formatDateTime accept string|undefined|null

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

web/src/pages/JobDetailPage.tsx

@@ -114,9 +114,9 @@ export default function JobDetailPage() {
               } />
             )}
             <InfoRow label="Attempts" value={`${job.attempts} / ${job.max_attempts}`} />
-            {job.error_message && (
+            {job.last_error && (
               <InfoRow label="Error" value={
-                <span className="text-red-600 text-xs">{job.error_message}</span>
+                <span className="text-red-600 text-xs">{job.last_error}</span>
               } />
             )}
           </div>