fix(templates): cross-validate against official Gitea mail templates

- Fix INK theme: replace .ActiveCodeLives with correct field, remove from non-auth contexts (8 files)
- Fix hardcoded button text: use locale key mail.view_it_on in ember, heritage, ink, mono, terminal, terra (30+ files)
- Add missing {{if .CanReply}}mail.reply{{end}} block to all 10 themes default.tmpl
- Add missing mail.release.note locale label to all 10 themes release.tmpl
- Add missing mail.team_invite.text_3 to ink and terra team_invite.tmpl
- Add missing blockquote CSS to aurora, ink, mono, neon, terra default.tmpl

Verified: all 110 templates compile successfully with Go build-preview.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

themes/horizon/mail/repo/issue/default.tmpl

@@ -71,7 +71,8 @@
           {{end}}
         {{else}}
           {{.Body}}
-        {{end -}}
+        {{end -}}{{if .CanReply}} {{.locale.Tr "mail.reply"}}{{end}}
+
         </p>
 
         {{- range .ReviewComments}}
@@ -118,7 +119,7 @@
         <p style="margin:0; font-size:14px; color:#64748b;">
           © <a href="{{AppUrl}}" target="_blank" rel="noopener noreferrer" style="color:#1e88e5; text-decoration:none; font-weight:500; border-bottom:1px dotted #b9d5f0;">{{AppName}}</a>
         </p>
-        <p style="margin:6px 0 0; font-size:12px; color:#94a3b8;">Secure notification – if you didn’t expect this, please ignore this email.</p>
+        <p style="margin:6px 0 0; font-size:12px; color:#94a3b8;">Secure notification – if you didn't expect this, please ignore this email.</p>
       </div>
 
     </div>