docs: Update AGENTS.md with comprehensive documentation

Commit notes

- Add missing backend routes: dashboard, mollie-connect, earnings, payouts - Add missing backend services: ai-cover-generation, mollie-connect, workspace-setup - Expand frontend components section with categorized tables: - Sequencer components (14 components) - Sample & library components (7 components) - Workspace & project components (4 components) - UI components (9 components) - User & subscription components (2 components) - Add Frontend Routes section with SvelteKit page documentation - Add Library Page Components subsection - Add API Client section documenting frontend/src/lib/api functions - Update monorepo structure to reflect dashboard and pack detail routes

Co-authored-by: armin.naimi <[email redacted]>