Document coding standards and add publisher helper foundation

[yusufbeGit]

Description

Updates the repository coding standards with clear comment, documentation, Astro component, and TypeScript formatting guidance. Also adds the publisher data-access helper foundation for upcoming publisher filtering work.

Related Issue

Closes #9

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• [✨] New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• [📚] Documentation update
• [🧪] Test update
• [🔧] Refactor (no functional changes)

Changes Made

• Added intent-focused comment and TSDoc/JSDoc standards to the Astro, Drizzle, and Copilot guidance.
• Documented reusable Astro component Props contracts and TypeScript formatting conventions.
• Linked the updated coding standards from the README.
• Added getAllPublishers with deterministic alphabetical ordering as the foundation for upcoming filtering work.
• Added publisher helper tests for ordering and empty results.
• Enforced indentation, quote, and semicolon rules for data-layer TypeScript through ESLint.

Testing

Data Layer Changes

• Ran npm run test:unit - all tests pass
• Added/updated Vitest tests for data-layer changes
• Generated a migration (npm run db:generate) for any schema change (not applicable; no schema changes)

Frontend Changes

• Ran npm run test:e2e - all tests pass
• Added data-testid attributes to interactive elements (not applicable; no UI changes)
• Verified build succeeds (npm run build)

Checklist

• My code follows the project's coding standards
• I have used explicit TypeScript types for function parameters and return values
• I have built the UI with Astro components and Tailwind CSS utility classes (not applicable; no UI changes)
• I have updated documentation (README, instruction files) if needed
• My changes are focused on a single concern
• I have written clear commit messages explaining what and why

Additional Notes

All executable quality checks pass: 29 unit tests, 21 E2E tests, lint, type checking, and the production build. Playwright MCP browser screenshots were unavailable in this session; this PR introduces no interactive UI changes.