Backups: stop double-opening the SQLite connection (silent write loss)

[AdaInTheLab]

Summary

Real bug, surfaced today during the first hands-on test of the backup feature.

What was wrong

`BackupService` had a redundant `conn.Open()` call inside every `using (var conn = _db.CreateConnection())` block — 6 occurrences across `CreateBackup`, `DeleteBackup`, `GetAll`, `GetBackup`, `LoadSettings`, `SaveSettings`. The factory already returns an opened connection, so this was opening twice.

The custom-built `System.Data.SQLite` we ship has a quirk on this code path:

• No exception thrown on the second Open
• Subsequent INSERT/UPDATE statements silently fail — the statement runs, returns affected-row counts, advances autoincrement counters, but nothing persists
• Reads aren't affected — SELECTs work normally

Effect:

• Click "Create Backup" → ZIP file appears on disk → controller returns `200 success` → no row in `backups` table → UI still says "No backups yet."
• Toggle Auto Backup on, click Save → `SaveSettings` silently drops the write → no `backup_settings` row in `settings` → scheduler never starts on next boot
• This made the entire feature look like it was wired but doing nothing

How it was caught

Patched `CreateBackup` with verbose logging on prod, clicked the button, log showed:
```
[BackupDebug] About to insert. Factory ConnString=Data Source=/...KitsuneCommand.db;Version=3;
[BackupDebug] conn type=System.Data.SQLite.SQLiteConnection state=Open db=main
[BackupDebug] INSERT rows=1 filename=backup_KitsuneDen_2026-05-09_06-43-35.zip
[BackupDebug] last_insert_rowid=2 total_rows_now=1
```

`last_insert_rowid=2` after a fresh table tells the story — earlier inserts had run far enough to advance the counter but never landed a row. Removing the second `.Open()` (which my diagnostic patch did as a side-effect of restructuring) made the INSERT persist.

Grep confirms this pattern is only in `BackupService` — all 19 other repositories use `_db.CreateConnection()` correctly.

Files

File	What
`Services/BackupService.cs`	Removed 6 redundant `conn.Open()` calls, added class-level doc comment explaining why

Test plan

• Pull, build, deploy
• Restart 7D2D
• Click "Create Backup" → audit list shows the new row immediately
• Toggle Auto Backup on, click Save → restart server → boot log shows `Backup scheduler started (every N min).`
• Wait one interval → next ZIP appears on disk + new row in audit list

🤖 Generated with Claude Code