fix: strip commas from email before contacts

[ElshadHu]

What Changed

Split msg.To by comma before saving so each recipient is saved individually. This also handles the trailing , the composer appends after suggestion selection. I skipped the empty parts from the split

I added comma trimming in AddContact just in case for persistence part

After all, I sent two emails to friend@floatpane.com, and checked out the contacts.json:

{
  "contacts": [
    {
      "name": "",
      "email": "friend@floatpane.com",
      "last_used": "2026-03-09T10:08:44.582981-04:00",
      "use_count": 2
    }
  ],
  "updated_at": "2026-03-09T10:08:44.582995-04:00"
}      

there is no duplicate. If there is any issue, please let me know 🙌.
Closes #251

[andrinoff]

Thank you for your contribution!

Will check in a few hours!