Visual improvements: UI polish across global, home, login, admin

[tilloh-dev]

Summary

• [global] Replaced emoji storage indicator with colored Carbon Cloud/CloudOffline icons inline in the header
• [global] Fixed letter-spacing not applying due to Carbon CSS token overrides
• [global] Fixed GlobalMenu showing apps with inactive toggles (getToggleValue now defaults to false)
• [global] Hidden header and redirect to home when no valid identifier is set
• [global] Refactored Carbon icon button centering into shared SCSS mixin carbon-icon-button
• [home] Replaced Navigation grid with time-based greeting component (morning/afternoon/evening/night, 3 variants each, DE + EN)
• [home] Added stale identifier validation on app load with E2E test
• [login] Added primary login button with Login icon next to password input
• [login] Refactored placeholder and showPasswordLabel into i18n
• [login] Login input row responsive: 40% desktop / 60% tablet / 95% mobile
• [admin] Fixed accordion list items not spanning full width

Test plan

• Login gate shown full-screen without header when not authenticated
• Invalid identifier in localStorage triggers re-login
• GlobalMenu only shows apps whose toggle is explicitly enabled
• Home greeting shows correct time-of-day variant with highlighted username
• Login input spans correct width on all screen sizes
• Admin accordion list items span full width with buttons at right edge

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