Enable demo mode features, auto-fill demo credentials, and enhance branding integration

- Added `DEMO_MODE` to backend configuration with relaxed security support for specific demo accounts.
- Updated password validators to allow predefined weak passwords in demo mode.
- Auto-fill login forms with demo credentials via query parameters for improved demo accessibility.
- Introduced demo user creation logic during database initialization if `DEMO_MODE` is enabled.
- Replaced `img` tags with `next/image` for consistent and optimized visuals in branding elements.
- Refined footer, header, and layout components to incorporate improved logo handling.

frontend/src/components/home/HeroSection.tsx

@@ -124,8 +124,6 @@ export function HeroSection({ onOpenDemoModal }: HeroSectionProps) {
               </Link>
             </Button>
           </motion.div>
-
-
         </div>
       </div>
     </section>