Fix data loss: remove data files from git, add gitignore, auto-recover

- Remove data/companies.json and data/companies/cuitunet/config.json from git
  (tracked data files get overwritten on every deploy, causing data loss)
- Add data/companies/*/ and data/tickets.json to .gitignore
- Migration now auto-recovers companies.json and config.json if missing
  (handles case where git clean removes untracked data files)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

data/companies.json

@@ -1,8 +0,0 @@
-[
-    {
-        "id": "cuitunet",
-        "nimi": "CuituNet",
-        "luotu": "2026-03-10 08:58:43",
-        "aktiivinen": true
-    }
-]

data/companies/cuitunet/config.json

@@ -1,4 +0,0 @@
-{
-    "mailboxes": [],
-    "ticket_rules": []
-}