Pi: minimal self-contained compose project (D-125)

The Kvitt Pi runs Kvitt from /home/jacobhagstedt/kvitt: compose.yaml, .env,
secrets/ and relative bind mounts ./data, ./backups, ./import. Both containers
run as the owner's uid/gid (KVITT_UID, KVITT_GID). No install script, no /opt,
no Docker daemon or system changes; operations are plain docker compose
commands (README "Pi: what the owner does", RESTORE.md).

Removed install.sh, deploy.sh, bootstrap.sh, backup-now.sh, install-apk.sh,
lib.sh. .env holds only the keys compose.yaml reads; RCLONE_REMOTE is fixed
to gdrive: in compose.yaml.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TQd3pEP9UeN2uifbHknQ7B

infra/pi/.gitignore

@@ -1,5 +1,5 @@
-# Filled on the Mac or the Pi, never committed: host addresses and registry credentials.
+# Filled on the Mac, never committed: the Pi's .env (host address) and the secrets staged for the copy to the Pi.
 .env
-# publish-apk.sh output (APKs, latest.json, R8 mappings) and secrets staged for the copy to the Pi.
-out/
 secrets/
+# publish-apk.sh output (APKs, latest.json, R8 mappings).
+out/