chore: Add .dockerignore to speed up builds

Excludes node_modules, .next, .git, env files, and other
unnecessary files from Docker build context.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.dockerignore

@@ -0,0 +1,44 @@
+# Dependencies
+node_modules
+.pnp
+.pnp.js
+
+# Build outputs
+.next
+out
+build
+dist
+
+# Testing
+coverage
+
+# Environment files (secrets!)
+.env
+.env.*
+!.env.example
+
+# IDE
+.idea
+.vscode
+*.swp
+*.swo
+
+# OS
+.DS_Store
+Thumbs.db
+
+# Git
+.git
+.gitignore
+
+# Logs
+*.log
+npm-debug.log*
+yarn-debug.log*
+yarn-error.log*
+
+# Misc
+*.md
+!README.md
+LICENSE
+deploy/