Dashboard Shell UI & Merchant Setup Flow

[aabxtract]

Overview

This PR introduces a major visual overhaul of the Invoisio dashboard shell to provide a premium, dynamic merchant workspace, along with a complete backend setup flow for merchants to configure their payout and profile details securely.

What's Changed

🎨 Frontend: Premium Dashboard Shell

Transformed the basic scaffolding into a responsive, polished UI with dark-mode styling and fluid micro-animations.

• Design System (globals.css): Introduced 40+ CSS tokens defining a deep navy palette, glassmorphism (backdrop-filter: blur), and comprehensive keyframe animations.
• Collapsible Sidebar (sidebar.tsx): Upgraded to support a smooth toggle between full (260px) and icon-only (72px) modes. Added a slide-in mobile drawer with a backdrop.
• Wallet-Aware Header (header.tsx): Rebuilt using glassmorphism. Includes breadcrumbs, a Stellar Testnet status badge, a pulsing auth status pill, and a responsive wallet balance card showing XLM/USDC with fiat equivalents.
• Dynamic Layout (dashboard-layout.tsx): Engineered with a unified SidebarProvider context that adjusts main content padding automatically based on the sidebar's collapse state.
• Polished Loading State (require-auth.tsx): Replaced the basic spinner with a customized shimmer skeleton that mimics the exact layout of the dashboard shell to prevent layout shift.

⚙️ Backend: Merchant Setup Flow

Enabled campaign contributors to test against realistic account data by establishing the merchant setup/profile lifecycle.

• Schema Upgrades (schema.prisma): Added businessEmail, preferredAsset, and payoutWallet fields to the Merchant model. Applied database migrations successfully.
• Strict Validation (is-stellar-public-key.validator.ts): Built a custom class-validator decorator utilizing @stellar/stellar-sdk's StrKey.isValidEd25519PublicKey. This securely rejects malformed or invalid Stellar addresses at the routing boundary.
• Profile Endpoints (merchant.controller.ts):
  • GET /merchants/:merchantId/profile: Fetch the current profile.
  • PATCH /merchants/:merchantId/profile: Update configurations (using UpdateMerchantProfileDto).
  • Protected using existing JwtAuthGuard and RBAC decorators.
• Module Registration (merchant.module.ts): Wired up the isolated MerchantModule directly into AppModule so the application can finally serve these endpoints.

Testing Instructions

1. Run npm install in both /web and /backend.
2. Apply migrations locally via npx prisma migrate dev.
3. In /web, view the dashboard across desktop (1440px), tablet (768px), and mobile (375px) breakpoints to verify the sidebar collapse and hamburger drawer.
4. Using an API client (like Postman), attempt a PATCH to the profile endpoint with an invalid payoutWallet (e.g., "G123INVALID") and ensure it returns a 400 Bad Request. Pass a valid Ed25519 public key and ensure it returns 200 OK.

closes #152
closes #157

[Cedarich]

@aabxtract please resolve merge conflicts

Also fix failing workflow