refactor: standardize workspace layouts and sidebar architecture

[chenyme]

Summary

Refactor the frontend workspace layout and sidebar navigation to improve module ownership, code organization, interaction consistency, and maintainability without changing existing APIs or user workflows.

Key changes:

• Reorganized shared conversation capabilities under entities/conversation, including sidebar state, conversation list rules, sharing, and export behavior.
• Removed Layouts dependencies on private Chat and Recent feature implementations.
• Simplified workspace composition and removed unnecessary wrapper components, hooks, and prop chains.
• Consolidated project conversation loading and navigation state behind Layouts-specific hooks.
• Simplified project, recent, starred, search, and conversation item implementations while preserving intentional icon animations.
• Improved sidebar expanded/collapsed transitions, selected states, row hover behavior, icon spacing, and section alignment.
• Fixed project and conversation action visibility so parent selection does not incorrectly activate child actions.
• Improved collapsed user menu alignment and normalized dropdown icon colors and submenu arrow sizing.
• Added feature public APIs where needed to preserve clear module boundaries.
• Removed the temporary Layouts-only ESLint semicolon rule to avoid feature-specific lint behavior.

Change type

• Bug fix
• Feature
• Documentation
• Refactor
• Configuration / deployment
• Security hardening
• Other

Affected areas

• Frontend / UI
• Backend / API
• Authentication / authorization
• Conversations / streaming
• Files / RAG / extraction
• Model routing / providers
• MCP / tools
• Billing / payments
• Admin console
• Deployment / Docker / configuration
• Documentation

Verification

• cd frontend && pnpm lint
• cd frontend && pnpm build
• Scoped git diff --check
• Manually checked sidebar expanded and collapsed states.
• Manually checked project, recent, starred, and conversation row interactions.
• Manually checked row hover, inline actions, selected states, and icon animations.
• Manually checked user dropdown positioning and nested dropdown menus.

Screenshots, API examples, or logs

Sidebar UI was manually reviewed in both expanded and collapsed states, including:

• Navigation and project alignment.
• Project and conversation hover states.
• Inline action visibility.
• Starred section animation.
• User dropdown positioning.
• Nested dropdown menu icons.

No API request or response changes are included.

Configuration, migration, and compatibility notes

No environment variables, database schema, deployment configuration, public URLs, or backend API contracts were changed.

The changes reorganize internal frontend module ownership and imports. Existing routes, authentication guards, conversation operations, and user-facing workflows remain compatible.

Documentation

• Documentation is not needed for this change.
• Documentation was updated.
• Documentation still needs to be updated.

Security and privacy

• No secrets, tokens, credentials, local config, or personal data are included.
• User data access remains scoped by authenticated user context unless an admin-only path explicitly requires broader access.
• Existing authentication guards and user-scoped conversation access behavior were preserved.

Checklist

• I searched existing issues and pull requests.
• Changes are focused and do not include unrelated refactors.
• Tests or static verification were run where practical.
• User-facing behavior, deployment steps, API contracts, or configuration changes are documented.
• Generated artifacts are included only when this project explicitly requires them.
• Caches, build output, .pyc files, .env files, and local storage data are not committed.