[FEATURE] Backup: Towers of Hanoi rotation strategy

[mkf-sysangels]

What's needed and why?

The current backup system supports only simple FIFO rotation: keep the N most recent files and delete the rest. This gives uniform time coverage — if you keep 7 daily backups, you can restore to any of the last 7 days, but no further.

A Towers of Hanoi rotation strategy provides exponentially increasing coverage without a proportional increase in storage. Recent backups are kept at high granularity; older backups are kept at progressively coarser intervals. This means:

• More recovery options near the present — ideal for catching recent misconfigurations or accidental changes
• Long-term coverage at low cost — with 24 files you cover ~85 days, versus 24 days with simple FIFO
• Predictable storage use — the file count is fixed regardless of how long the system runs

Proposed tier structure (24 files, ~85 days coverage):

Tier	Slots	Interval	Covers
1	6	1 h	last 6 h
2	2	2 h	6–10 h ago
3	2	4 h	10–18 h ago
4	2	8 h	18–34 h ago
5	2	16 h	34–66 h ago
6	2	32 h	66–130 h ago
7	2	64 h	130–258 h ago
8	2	128 h	258–514 h ago
9	2	256 h	514–1026 h ago
10	2	512 h	1026–2050 h ago (~85 days)

Implementations ideas (optional)

• Add hanoi as a new option for BACKUP_SCHEDULE. When selected, the job creates a backup every hour and applies the ToH rotation after each run. Existing schedules (daily, weekly, monthly) are unaffected.
• Change the job's "every" field in plugin.json from "day" to "hour". The existing already_done guard prevents extra backups for daily/weekly/monthly users, so this is backward-compatible.
• Add a hanoi_rotation(backup_files, now) utility function to backup.py. It walks backwards from now through the tier windows and returns the files to delete — keeping the most recent backup that falls within each slot.
• BACKUP_ROTATION is ignored when BACKUP_SCHEDULE=hanoi; the tier counts are the effective limit.

Code of Conduct

• I agree to follow this project's Code of Conduct

[mkf-sysangels]

This will change the backup job to run hourly to keep the latest 6 hours in the queue.

The Towers of Hanoi logic will then clean up older backups to match the intervall.

[mkf-sysangels]

Set BACKUP_SCHEDULE=hanoi to enable the new feature

[mkf-sysangels]

New:

• Before each backup a disk-space pre-flight check is performed to ensure sufficient free space.
• Each backup ZIP contains the SQL dump and a SHA-256 checksum file (.sha256) for integrity verification.
• Old backups are automatically rotated based on your retention settings. The hanoi schedule uses Towers of Hanoi rotation (24 files, ~85 days of coverage) instead of a simple count.
• Verify SHA-256 checksums of all backups: bwcli plugin backup check
• SQLite WAL mode: readers and writers do not block each other, so the dump can run without holding the BunkerWeb lock at all.
• Optimized Database-Locking (time of DB-lock from ~20 sec to ~2 sec on not WAL enabled SQLite)