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/layout/DmSearchBar.tsx

@@ -370,7 +370,7 @@ export function DmSearchBar() {
             onChange={(e) => { setQuery(e.target.value); setSelectedIndex(0); }}
             onKeyDown={handleKeyDown}
             placeholder="Search..."
-            className="flex-1 min-w-0 bg-transparent text-txt-primary placeholder-txt-tertiary/60 text-[13px] font-medium outline-none py-[5px]"
+            className="input-embedded flex-1 min-w-0 text-[13px] font-medium py-[5px]"
           />
         </div>
       ) : (