feat: proper logo, favicon, and pwa icons

- replace placeholder house svg with clean geometric house mark
  on indigo-700 (#4338CA) — roof triangle, body, door cutout
- add favicon.svg with prefers-color-scheme dark variant
- add icon-16/32 sizes; regenerate all pngs from svg via sharp
- update BrandMark component to use inline svg house instead of 'f'
- wire favicon + sized pngs into layout metadata
- fix middleware to allow icon/manifest/favicon paths without auth
  (android launcher fetches icons in a cookieless system context)
- fix getCurrentSession() to redirect to /login instead of throwing
  when session cookie is stale/invalid

src/components/brand-mark.tsx

@@ -1,12 +1,23 @@
 import { cn } from "@/lib/utils";
 
 export function BrandMark({ size = "md", className }: { size?: "sm" | "md"; className?: string }) {
+  const iconSize = size === "sm" ? 14 : 17;
   return (
     <span
       className={cn("brand-mark", size === "sm" && "brand-mark-sm", className)}
       aria-hidden="true"
     >
-      f
+      <svg
+        viewBox="0 0 24 24"
+        xmlns="http://www.w3.org/2000/svg"
+        width={iconSize}
+        height={iconSize}
+        fill="currentColor"
+      >
+        <polygon points="12,2 1,12 23,12" />
+        <rect x="3.5" y="11" width="17" height="12" />
+        <rect x="9.5" y="16" width="5" height="7" rx="1" style={{ fill: "var(--ink)" }} />
+      </svg>
     </span>
   );
 }