v0.2.0

v0.2.0 — accounts and settings

Added

• Acceder in the header opens a login box; signed in it becomes Ajustes.
• A settings page: profile, password, theme, accounts, default notation. It
  carries no library navigation.
• Two roles. Everyone may edit songs; an administrator manages accounts.
• Generar cancionero: pick any set of songs and print them as one document, each
  in the key you asked it to remember.
• Import and export are reachable from the settings page instead of only by
  typing /import.
• A light or dark theme per account, following you between devices.

Accounts

• Reading stays public. Writing needs an account once the instance is claimed.
• An instance with no accounts behaves as before and says so, so an existing
  collection upgrades without surprises.
• Accounts live in data/accounts.json, not in the index. Back it up: it is the
  one file there that cannot be rebuilt.
• Claim it from the browser, or set TABERNACLE_ADMIN_USER and
  TABERNACLE_ADMIN_PASSWORD. Setting them again resets that password.
• PBKDF2 from the standard library. No new dependency.
• Sessions are signed cookies with no server-side table, so they survive both a
  restart and deleting the index.

Docs

• docs/accounts.md: threat model, file format, recovery, and what is deliberately
  absent.
• The backup instructions now mention accounts.json.