Add full application: receipt scanning, auth, billing, and account deletion

Brings the working codebase (Next.js app, auth system, Stripe billing,
Docker/deploy config, tests, docs) into version control on top of the
placeholder initial commit, and adds account self-deletion (Danger Zone
in Settings, password + typed-email confirmation, cascading DB cleanup,
Stripe cancellation) per GDPR right-to-erasure.

Excludes local build caches, node_modules, and internal agent scratch
files; .gitignore hardened to keep those out going forward.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

docker-entrypoint-logs.sh

@@ -0,0 +1,15 @@
+#!/bin/sh
+set -e
+
+# The admin dashboard's "Docker Logs" page needs the app process (which drops
+# to the unprivileged "nextjs" user below) to read /var/run/docker.sock. Group
+# membership isn't a reliable way to grant that: on Docker Desktop the
+# socket's group id was observed to change across restarts (0 one time, 1001
+# the next) on the same host. Chmod'ing it wide open here — while this
+# container still starts as root, before the privilege drop — sidesteps that
+# entirely. No-op if the socket isn't mounted (e.g. bare `npm run dev`).
+if [ -S /var/run/docker.sock ]; then
+  chmod 666 /var/run/docker.sock || true
+fi
+
+exec su-exec nextjs "$@"