feat(17-02): Dockerfile three-stage build, .dockerignore, .env.production.example

- Three-stage node:20-slim Dockerfile with --platform=linux/amd64 on all 3 FROM lines
- Non-root nextjs:nodejs user, seeds/ copied for form library, uploads/ dir pre-created
- HEALTHCHECK via wget pointing to /api/health, CMD node server.js
- .dockerignore excludes node_modules, .next, .git, .env*, uploads/, *.md
- .env.production.example with exactly 11 required vars (template, no real secrets, force-added past .env* glob)

teressa-copeland-homes/.dockerignore

@@ -0,0 +1,12 @@
+node_modules
+.next
+.git
+.env*
+uploads/
+*.md
+.DS_Store
+.vscode
+.idea
+npm-debug.log*
+scripts/*.png
+drizzle/meta