feat: standardize input styling with tier system, add depth and admin features

- Define 4 input tier CSS classes (input-standard, input-search, input-embedded, input-danger)
  in globals.css, migrating ~50 inputs across ~28 component files to use them
- Add subtle border and inset shadow to solid input tiers for resting-state visibility
- Fix focus ring clipping in settings panel scroll container
- Fix phantom Tailwind tokens (border-border-primary, placeholder-txt-muted)
- Add admin user management panel, storage management, and account deletion utilities

packages/web/src/components/ui/Avatar.tsx

@@ -102,7 +102,7 @@ export function Avatar({ src, name, size = 40, status, className = '', onClick,
       >
         {src ? (
           <img
-            src={(src.startsWith('http') || src.startsWith('blob:') || src.startsWith('data:'))
+            src={(src.startsWith('http') || src.startsWith('blob:') || src.startsWith('data:') || src.startsWith('/'))
               ? src : `/api/uploads/${src}`}
             alt={name}
             loading="lazy"

packages/web/src/components/ui/UserProfilePopout.tsx

@@ -68,7 +68,7 @@ export function UserProfilePopout({ user, onClose, position }: UserProfilePopout
 
   // Banner display
   const bannerSrc = user.banner
-    ? (user.banner.startsWith('http') ? user.banner : userApi.uploads.url(user.banner))
+    ? (user.banner.startsWith('http') || user.banner.startsWith('/') ? user.banner : userApi.uploads.url(user.banner))
     : null;
   const bannerFallback = user.accentColor
     ? mutedGradient(user.accentColor, adjustColor(user.accentColor, -40))