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>

.dockerignore

@@ -0,0 +1,19 @@
+node_modules
+.next
+.git
+.agents
+.vscode
+.idea
+*.log
+.env
+.env.local
+.env*.local
+build_err.txt
+npm-debug.log*
+tests
+drizzle
+*.tsbuildinfo
+Dockerfile
+docker-compose.yml
+.dockerignore
+README.md