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>

.dockerignore

@@ -0,0 +1,10 @@
+*
+!server.py
+!index.html
+!app.js
+!theme.js
+!crypto-fallback.js
+!styles.css
+!favicon.svg
+!banks/*.svg
+!vendor/**