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/terminal/mail/repo/transfer.tmpl

@@ -38,8 +38,7 @@
         </table>
 
         <div style="background:#0d1117; border:1px solid #30363d; padding:14px 16px; margin:20px 0 12px;">
-          <p style="margin:0 0 6px; font-size:12px; color:#8b949e;">
-            {{.locale.Tr "mail.link_not_working_do_paste"}}
+          <p style="margin:0 0 6px; font-size:12px; color:#8b949e;"><span style="color:#8b949e;">{{.locale.Tr "mail.link_not_working_do_paste"}}</span>
           </p>
           <p style="margin:0; font-size:12px; color:#58a6ff; word-break:break-all; line-height:1.6;">
             ┌─<br>