Initial commit: Setup CargoTrace monorepo

- Add README.md with project overview
- Add .gitignore for IDE and OS files
- Add Flutter Android app as submodule (apps/pad_scanner)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.gitignore

@@ -0,0 +1,15 @@
+# IDE
+.idea/
+.vscode/
+*.swp
+*.swo
+*~
+
+# OS
+.DS_Store
+Thumbs.db
+
+# Project specific
+*.log
+.env
+.env.local