Fix/auto generate jwt secret (#94)

* fix: auto-generate JWT_SECRET at startup if not provided
- Add ensureJwtSecret() in instrumentation.ts to generate random 64-char secret
- Mark JWT_SECRET as non-required in secretsValidator
- Remove fatal error log for missing JWT_SECRET in proxy.ts
Fixes login failure when running via CLI without JWT_SECRET env var.

* feat: improve auth flow and login page UX
- Add setupComplete to settings validation schema for proper persistence
- Support ?tab= query param in settings page for direct tab navigation
- Redesign login page with professional two-column layout
- Add context-aware states for onboarding/password setup flows
- Smooth animations and refined visual hierarchy

* fix: 404 page to use primary color theme (coral red) instead of purple

src/shared/validation/schemas.ts

@@ -69,6 +69,7 @@ export const updateSettingsSchema = z.object({
   logRetentionDays: z.number().int().min(1).max(365).optional(),
   cloudUrl: z.string().max(500).optional(),
   baseUrl: z.string().max(500).optional(),
+  setupComplete: z.boolean().optional(),
 });
 
 // ──── Auth Schemas ────