feat: add AI Dental Shopping section with sidebar nav and Login Info page

- Add AI Dental Shopping to sidebar with Search/Tag and Login Info sub-pages
- Build full-stack Login Info CRUD: save vendor name, website, username, password per user
- Add ShoppingVendor Prisma model, run db push, regenerate client and Zod schemas
- Add storage layer, REST API at /api/shopping-vendors/, and frontend table with add/edit/delete modal

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

packages/db/shared/schemas/variants/input/User.input.ts

@@ -12,6 +12,7 @@ export const UserInputSchema = z.object({
     npiProviders: z.array(z.unknown()),
     claims: z.array(z.unknown()),
     insuranceCredentials: z.array(z.unknown()),
+    shoppingVendors: z.array(z.unknown()),
     updatedPayments: z.array(z.unknown()),
     backups: z.array(z.unknown()),
     backupDestinations: z.array(z.unknown()),