ci: add dependabot configuration for automated dependency updates

[Copilot]

Configures Dependabot to automatically create PRs for dependency updates across all package ecosystems in the repository.

Configuration

• npm: Root project and docs-site/ with grouping for TypeScript, testing, linting, and commitlint dependencies
• Docker: Base image updates for containers/agent/ and containers/squid/
• GitHub Actions: Workflow action version updates with grouping for actions/*

Schedule

Weekly on Mondays with reasonable PR limits per ecosystem to avoid noise.

Grouping Rules

Related dependencies are bundled to reduce PR churn:

• typescript, @types/*, @typescript-eslint/*, ts-*
• jest, *jest*
• eslint, *eslint*
• @commitlint/*, husky
• astro, @astrojs/*

Original prompt

---

This section details on the original issue you should resolve

<issue_title>[High Priority] Enable Dependabot for automated dependency updates</issue_title>
<issue_description>## Context
From CI/CD Pipeline Gap Assessment (Discussion #227)

Description

Configure Dependabot to automatically create PRs for dependency updates, improving security and maintainability.

Acceptance Criteria

• Create dependabot configuration file
• Configure npm ecosystem scanning
• Set appropriate update schedule (e.g., weekly)
• Configure grouping rules for related dependencies
• Add Docker ecosystem scanning for container images

Estimated Effort

Approximately 30 minutes

Related

• Discussion CI/CD Pipeline and Integration Tests - Gap Assessment #227</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes [High Priority] Enable Dependabot for automated dependency updates #233

---

💬 We'd love your input! Share your thoughts on Copilot coding agent in our 2 minute survey.

[github-actions]

Test Coverage Report

Metric	Coverage	Covered/Total
Lines	77.19%	1300/1684
Statements	77.27%	1333/1725
Functions	77.17%	142/184
Branches	69.76%	450/645

Coverage Thresholds

The project has the following coverage thresholds configured:

• Lines: 38%
• Statements: 38%
• Functions: 35%
• Branches: 30%

---

Coverage report generated by `npm run test:coverage`