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>

tools/data/templates_config.json

@@ -141,7 +141,7 @@
         "ActionName": "comment",
         "Doer": { "Name": "Sarah Chen" },
         "Body": "This is a comment on the issue with details about the fix.",
-        "CanReply": true,
+        "CanReply": false,
         "IsMention": false,
         "IsPull": false,
         "Issue": {