Fix garbled ticket text from HTML emails (Outlook VML/entities)

extractBody() used a naive tag-stripping regex as a fallback, which
strips <style> tags but leaves their CSS content behind as visible
text, and never decodes HTML entities. Outlook's VML style block
(v\:* {behavior:url(#default#VML);} ...) and &nbsp;/&laquo; entities
were leaking straight into ticket bodies as a result.

Now uses html-to-text (already a transitive dep via mailparser,
promoted to direct) to convert the HTML part whenever present, which
correctly drops <head>/<style> content and decodes entities. Also
stopped trusting parsed.text unconditionally — some senders' plain-text
alternative isn't actually clean, so HTML is now the primary source
whenever available.

package-lock.json

@@ -12,6 +12,7 @@
         "better-sqlite3": "^12.11.1",
         "drizzle-orm": "^0.45.2",
         "framer-motion": "^12.4.7",
+        "html-to-text": "^10.0.0",
         "imapflow": "^1.5.0",
         "ldapjs": "^3.0.7",
         "lucide-react": "^0.545.0",