feat: complete vendor frontend parity with admin

Phase 1 - Sidebar Refactor:
- Refactor sidebar to use collapsible sections with Alpine.js
- Add localStorage persistence for section states
- Reorganize navigation into logical groups

Phase 2 - Core JS Files:
- Add products.js: product CRUD, search, filtering, toggle active/featured
- Add orders.js: order list, status management, filtering
- Add inventory.js: stock tracking, adjust/set quantity modals
- Add customers.js: customer list, order history, messaging
- Add team.js: member invite, role management, remove members
- Add profile.js: profile editing with form validation
- Add settings.js: tabbed settings (general, marketplace, notifications)

Templates updated from placeholders to full functional UIs.
Vendor frontend now at ~90% parity with admin.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

mkdocs.yml

@@ -166,6 +166,7 @@ nav:
       - Unified Order View: implementation/unified-order-view.md
       - VAT Invoice Feature: implementation/vat-invoice-feature.md
       - OMS Feature Plan: implementation/oms-feature-plan.md
+      - Vendor Frontend Parity: implementation/vendor-frontend-parity-plan.md
 
     # --- Testing ---
     - Testing: