chore: final cleanup

Remove tracked .DS_Store, add .dockerignore, and ignore app-specific env file.

.dockerignore

@@ -0,0 +1,24 @@
+node_modules
+**/node_modules
+.next
+**/.next
+.env.local
+.env
+.git
+.gitignore
+*.log
+.DS_Store
+coverage
+.vscode
+.idea
+dist
+.cache
+.turbo
+**/.turbo
+.tsbuildinfo
+*.md
+!README.md
+tests
+**/*.test.*
+playwright.config.ts
+vitest.config.mts