Add Dependabot configuration for all 4 languages

[thatsjet]

Summary

Automated dependency updates to catch security vulnerabilities in dependencies (PyYAML, js-yaml, Jackson, etc.).

Instructions

Create .github/dependabot.yml

version: 2
updates:
  - package-ecosystem: "pip"
    directory: "/python"
    schedule:
      interval: "weekly"
    labels:
      - "dependencies"

  - package-ecosystem: "npm"
    directory: "/nodejs"
    schedule:
      interval: "weekly"
    labels:
      - "dependencies"

  - package-ecosystem: "gomod"
    directory: "/golang"
    schedule:
      interval: "weekly"
    labels:
      - "dependencies"

  - package-ecosystem: "maven"
    directory: "/java"
    schedule:
      interval: "weekly"
    labels:
      - "dependencies"

  - package-ecosystem: "github-actions"
    directory: "/"
    schedule:
      interval: "weekly"
    labels:
      - "dependencies"

Verification

• File exists at .github/dependabot.yml
• YAML is valid
• After push, Dependabot should create PRs for any outdated dependencies within a few hours