feat: redesign docs site pages, migrate legal/about to App Router, add feedback widget (#502)

* feat: update table of content style in DocsPage component

* feat: add feedback widget, redesign DocsHub, and add sidebar logo

* feat: update demo images for dark and light themes

* feat: update demo images for dark and light themes

* feat: replace logo image and remove duplicate SVG file

* feat: add LocalInstallHub component and update documentation for local installation

* feat: enhance UI by updating feature icons and descriptions, and improving layout responsiveness

* Add legal pages: Cookie Policy, Privacy Policy, and Terms of Service

- Implemented Cookie Policy page with details on cookie usage and user privacy.
- Created Privacy Policy page outlining data collection practices and user rights.
- Developed Terms of Service page defining the usage terms for the documentation site.
- Removed outdated MDX files for cookie, privacy, and terms of service.
- Updated FeaturesHub component to include new feature highlights and improved layout.

* feat: enhance GitHub data fetching to include contributor count and update CommunitySection layout

.env.template

@@ -1,3 +1,13 @@
+# Docs feedback (GitHub Discussions + Discord)
+# GitHub personal access token with discussions:write scope (optional)
+GITHUB_FEEDBACK_TOKEN=
+# GitHub repository node ID — run: gh api graphql -f query='{repository(owner:"LibreChat-AI",name:"librechat.ai"){id}}'
+GITHUB_DISCUSSION_REPO_ID=
+# GitHub discussion category node ID — run: gh api graphql -f query='{repository(owner:"LibreChat-AI",name:"librechat.ai"){discussionCategory(slug:"feedback"){id}}}'
+GITHUB_DISCUSSION_CATEGORY_ID=
+# Discord webhook URL for real-time feedback notifications (optional)
+DISCORD_FEEDBACK_WEBHOOK=
+
 # Analytics and feedback
 # Slack webhook URL for notifications (optional)
 SLACK_WEBHOOK_URL=