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/JobsPage.tsx

@@ -139,9 +139,9 @@ export default function JobsPage() {
     {
       key: 'error',
       label: 'Error',
-      render: (j) => j.status === 'Failed' && j.error_message ? (
-        <span className="text-xs text-red-600 truncate max-w-[200px] inline-block" title={j.error_message}>
-          {j.error_message.length > 80 ? j.error_message.substring(0, 80) + '...' : j.error_message}
+      render: (j) => j.status === 'Failed' && j.last_error ? (
+        <span className="text-xs text-red-600 truncate max-w-[200px] inline-block" title={j.last_error}>
+          {j.last_error.length > 80 ? j.last_error.substring(0, 80) + '...' : j.last_error}
         </span>
       ) : <span className="text-xs text-ink-faint">—</span>,
     },