feat: add view-as-role feature for site admins (#15)

Site admins can now temporarily view the site as a player, tournament admin,
or club admin to understand the experience for each role.

Changes:
- Added RoleSwitcher context and provider for client-side role simulation
- Added role switcher dropdown in Navigation (visible only to site admins)
- Added yellow banner showing current viewing-as role with reset button
- Navigation links and wordmark href now use effective role for conditional display
- Added BDD feature file with 5 scenarios covering all role transitions
- Added step definitions for site admin login and role switcher interactions

The view-as feature is purely UI-level - server-side permissions remain unchanged.
5 scenarios, 27 steps, all passing.

e2e/cucumber/step-definitions/auth-steps.ts

@@ -158,6 +158,58 @@ Given('I am logged in as a tournament admin', async function () {
   console.log(`🌍 User created: ${credentials.email}`);
 });
 
+/**
+ * Precondition: I am logged in as a site admin
+ * Creates a new user and assigns site_admin role via Prisma
+ */
+Given('I am logged in as a site admin', async function () {
+  console.log('🌍 Creating and logging in as a site admin...');
+  
+  const credentials = generateTestCredentials();
+  world.user = credentials;
+  
+  await world.page.goto(`${world.baseURL}/auth/register`);
+  await world.page.waitForLoadState('domcontentloaded');
+  
+  await world.page.fill('input[name="name"]', credentials.name);
+  await world.page.fill('input[name="email"]', credentials.email);
+  await world.page.fill('input[name="password"]', credentials.password);
+  
+  await world.page.click('button[type="submit"]');
+  await world.page.waitForURL(/\/players\/\d+\/profile/, { timeout: 15000 });
+  
+  const currentUrl = world.page.url();
+  const match = currentUrl.match(/\/players\/(\d+)\/profile/);
+  if (match) {
+    const playerId = match[1];
+    world.playerId = playerId;
+    
+    const prisma = await world.getPrisma();
+    const player = await prisma.player.findUnique({
+      where: { id: parseInt(playerId) },
+      include: { user: true }
+    });
+    
+    if (player && player.user) {
+      const userId = player.user.id;
+      (world.user as any).id = userId;
+      
+      await prisma.user.update({
+        where: { id: userId },
+        data: { role: 'site_admin' }
+      });
+      console.log(`🌍 Assigned site_admin role to user: ${userId}`);
+      
+      // Navigate to home page to trigger Navigation re-mount with new role
+      await world.page.goto(`${world.baseURL}/`);
+      await world.page.waitForLoadState('networkidle');
+      await world.page.waitForTimeout(1000);
+    }
+  }
+  
+  console.log(`🌍 Site admin created: ${credentials.email}`);
+});
+
 /**
  * Precondition: I am logged in as a club admin
  * Uses a pre-existing admin user from the database