Start LibreLedger: an encrypted money ledger that stores only ciphertext

LibreLedger is a single-person money ledger. The browser encrypts
everything (PBKDF2-HMAC-SHA256 with 250k iterations, then AES-256-GCM),
and a small standard-library Python server stores only the resulting
{v, salt, iv, ct} blob. Ledger files from the earlier Money Ledger version
open unchanged.

- On plain http to a LAN or VPN address, where browsers hide Web Crypto,
  the app switches to vendored @noble/hashes and @noble/ciphers 2.2.0 and
  says so on the lock screen. tests/crypto-interop.test.mjs shows both
  paths read each other's files.
- The server hands out only the app's own files, sends a self-only CSP,
  nosniff, frame denial and no-referrer, checks the shape of each blob,
  refuses cross-site writes and writes atomically. It keeps the last 10
  backups plus one per day for 30 days.
- The container runs that server from a digest-pinned python alpine
  image, as an unprivileged user, with its data in /data and a health
  check on /api/health.

Assisted-by: Claude Opus 5 <noreply@anthropic.com>

.gitignore

@@ -0,0 +1,21 @@
+# Encrypted ledger data: never commit it, even though it is encrypted
+data/
+*.enc
+*.enc.bak
+*.enc.*
+
+# Local design-reference screenshots may contain real figures
+preview.png
+
+# Local Claude Code settings
+.claude/
+
+# Test output and caches
+tests/out/
+__pycache__/
+*.pyc
+
+# OS / editor cruft
+.DS_Store
+Thumbs.db
+*.swp