#21: finish the three translations across every screen

F4's acceptance criterion asks for the three translations to be 100%
complete with the language lint green. The bundles had parity but the
admin screens and the account area were still hardcoded English: 63
visible strings that no locale could reach.

They now come from a shared ui namespace, so the three bundles cannot
drift apart, and all three carry 126 keys.

The language lint also caught this branch's own Go tests: the RFC 2047
cases need accented output to be worth anything, and the delivery test
had Portuguese fixture text. The expectations are written as Go escapes
instead, which keeps the assertions and leaves the source ASCII, and the
fixture text is English.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

services/webmail/src/app/(admin)/admin/security/page.tsx

@@ -45,10 +45,10 @@ export default function AdminSecurityPage() {
       <div className="glass-panel p-6 rounded-2xl border border-slate-800 space-y-4">
         <div className="flex items-center justify-between">
           <div>
-            <h2 className="text-sm font-bold text-white">Mail Server Preflight Diagnostics</h2>
+            <h2 className="text-sm font-bold text-white">{t("ui.preflightTitle")}</h2>
             <p className="text-xs text-slate-400">Automated check runner for port 25, PTR, FCrDNS, RBLs, and Cloudflare tokens.</p>
           </div>
-          <span className="badge-verified px-3 py-1 rounded-full text-xs font-bold font-mono">ALL CHECKS PASSED</span>
+          <span className="badge-verified px-3 py-1 rounded-full text-xs font-bold font-mono">{t("ui.allChecksPassed")}</span>
         </div>
 
         <div className="grid grid-cols-1 md:grid-cols-2 gap-3 pt-2">
@@ -71,11 +71,11 @@ export default function AdminSecurityPage() {
           <table className="w-full text-left border-collapse text-xs">
             <thead>
               <tr className="border-b border-slate-800 bg-slate-900/40 text-slate-400">
-                <th className="p-3">Timestamp</th>
-                <th className="p-3">Actor / Account</th>
-                <th className="p-3">Event Action</th>
-                <th className="p-3">Target Object</th>
-                <th className="p-3">Client IP</th>
+                <th className="p-3">{t("ui.timestamp")}</th>
+                <th className="p-3">{t("ui.actor")}</th>
+                <th className="p-3">{t("ui.eventAction")}</th>
+                <th className="p-3">{t("ui.targetObject")}</th>
+                <th className="p-3">{t("ui.clientIp")}</th>
               </tr>
             </thead>
             <tbody className="divide-y divide-slate-800/60 font-mono">