fix(templates): add inline colors for dark-background themes, set CanReply=false

- aurora, neon, terminal: add explicit inline color styles to bare
  text elements (locale.Tr calls, h4 headings, download labels)
  that were invisible in clients stripping <style> blocks (Gmail).
  33 files across 3 dark-background themes.
- CanReply: changed from true to false in mock data — matches
  typical Gitea deployment where IncomingEmail is disabled by
  default. Template syntax kept identical to official Gitea.

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

themes/aurora/mail/user/auth/register_notify.tmpl

@@ -42,7 +42,7 @@
           <a href="{{AppUrl}}user/login" style="display:inline-block;padding:16px 48px;font-size:14px;font-weight:400;color:#e0f5f3;text-decoration:none;background:rgba(13,148,136,0.18);border:1px solid rgba(13,148,136,0.3);letter-spacing:1px;">Go to {{AppName}}</a>
         </td></tr></table>
         <table width="100%" cellpadding="0" cellspacing="0" border="0" style="border:1px solid rgba(13,148,136,0.18);background:rgba(13,148,136,0.03);"><tr><td style="padding:16px 18px;">
-          <p style="margin:0 0 8px;font-size:11px;color:rgba(180,252,238,0.75);font-weight:300;">{{.locale.Tr "mail.link_not_working_do_paste"}}</p>
+          <p style="margin:0 0 8px;font-size:11px;color:rgba(180,252,238,0.75);font-weight:300;"><span style="color:rgba(180,195,215,0.95);">{{.locale.Tr "mail.link_not_working_do_paste"}}</span></p>
           <p style="margin:0;font-size:11px;font-family:monospace;color:#99f6e4;background:rgba(0,0,0,0.2);padding:10px 12px;border:1px solid rgba(13,148,136,0.15);word-break:break-all;">{{AppUrl}}user/login</p>
         </td></tr></table>
       </td></tr>