feat(web): adopt cyberspace terminal aesthetic + dithered images

Rebrand light/dark themes to the cyberspace.online look: warm cream-on-black
palette (light/dark are exact inverses), self-hosted JetBrains Mono + VT323,
square corners, border-driven surfaces with no soft shadows. Adds a terminal
design-system CSS layer (DOS double-border modals with hatched corner, fg focus,
inversion-on-hover), a theme-aware <RasterImage> (Atkinson-dithered canvas with
img fallback), and unifies desktop icons, taskbar, window controls, pills and
links under one idiom. Pins window titlebars to a fixed height and switches chat
auto-scroll off scrollIntoView to avoid titlebar reflow.

VERSION 0.15.1 -> 0.16.0

web/src/pages/Overview.svelte

@@ -99,9 +99,9 @@
       <button
         type="button"
         onclick={() => (filter = f.id)}
-        class="rounded-full border px-2.5 py-1 text-xs transition-colors {filter === f.id
-          ? 'border-primary bg-primary/10 text-foreground'
-          : 'border-border bg-card/60 text-muted-foreground backdrop-blur hover:bg-muted/50'}"
+        class="border px-2.5 py-1 text-xs transition-colors {filter === f.id
+          ? 'border-foreground bg-foreground text-background'
+          : 'border-border text-muted-foreground hover:border-foreground hover:text-foreground'}"
       >
         {f.label}
         <span class="ml-1 opacity-60">{counts[f.id] ?? 0}</span>