Add WhatsApp feature flag and improve onboarding

- Add getFeatureFlags endpoint to check if WhatsApp is enabled
- Skip phone step in onboarding when WhatsApp is disabled
- Hide WhatsApp notification options when disabled
- Add ExpertiseSelect component with predefined ocean conservation tags
- Fix onboarding layout to fill viewport on desktop

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

src/server/routers/settings.ts

@@ -19,6 +19,22 @@ function categorizeModel(modelId: string): string {
 }
 
 export const settingsRouter = router({
+  /**
+   * Get public feature flags (no auth required)
+   * These are non-sensitive settings that can be exposed to any user
+   */
+  getFeatureFlags: protectedProcedure.query(async ({ ctx }) => {
+    const [whatsappEnabled] = await Promise.all([
+      ctx.prisma.systemSettings.findUnique({
+        where: { key: 'whatsapp_enabled' },
+      }),
+    ])
+
+    return {
+      whatsappEnabled: whatsappEnabled?.value === 'true',
+    }
+  }),
+
   /**
    * Get all settings by category
    */