Fix high-severity Dependabot alerts (#2801)

## Summary
- **Go**: Update `buger/jsonparser` 1.1.1 → 1.1.2 (DoS fix)
- **Django**: Update 4.2.27 → 4.2.29 (SQL injection + uncontrolled
resource consumption fixes)
- **Rails example**: Upgrade Rails 7.1.5 → 7.2.0, bringing rack 2.2.14 →
3.2.5 (directory traversal + Active Storage path traversal fixes)
- **VS Code extension**: Add yarn resolutions to update minimatch 3.1.2
→ 3.1.5 (ReDoS) and serialize-javascript 6.0.2 → 7.0.4 (RCE via
RegExp.flags)

## Test plan
- [ ] Verify `go build ./...` still passes
- [ ] Verify VS Code extension compiles (`cd vscode-extension && yarn
compile`)
- [ ] Confirm Dependabot alerts close after merge

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

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