Add CI workflow for automated checks on pull requests

[Copilot]

• Create CI workflow for automated checks on pull requests
• Add security audit step with npm audit
• Add TypeScript and Astro validation step
• Add build verification step
• Use same Bun setup as deployment workflow
• Replace npm/npx commands with bun equivalents per feedback
  • Changed npm audit --audit-level=high to bun audit --audit-level=high
  • Changed npx astro check to bunx astro check

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[t128n]

@copilot Make sure to use bun instead of node.js

[Copilot]

@copilot Make sure to use bun instead of node.js

Updated the CI workflow to use bun commands instead of node.js:

• Changed npm audit --audit-level=high to bun audit --audit-level=high
• Changed npx astro check to bunx astro check

These changes ensure the CI workflow uses bun consistently throughout. (00e4d2e)