Enhance devcontainer and CI workflows

- Add persistent volume mounts for Go/npm caches (faster rebuilds)
- Add shell config with helpful aliases and custom prompt
- Add comprehensive devcontainer documentation
- Add pre-commit hooks for Go formatting and linting
- Use go-version-file in CI workflows instead of hardcoded versions
- Simplify docker compose commands with --wait flag
- Add gitignore entries for devcontainer auth files

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

.gitignore

@@ -178,3 +178,7 @@ landing-page/
 .gemini/
 deployment/
 start-pulse-agent.sh
+
+# Dev container extension auth
+.devcontainer/.claude/
+.devcontainer/.config/