feat: use cameleer3-logo.svg from design-system v0.1.36 everywhere

- Sidebar, sign-in page, and favicons all use the single SVG
- Postinstall copies SVG for SaaS HTML favicon (gitignored)
- Sign-in favicon committed (baked into Logto Docker image)
- Remove old PNG favicon references

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/src/components/Layout.tsx

@@ -8,7 +8,7 @@ import {
 import { useAuth } from '../auth/useAuth';
 import { useScopes } from '../auth/useScopes';
 import { EnvironmentTree } from './EnvironmentTree';
-import cameleerLogo from '@cameleer/design-system/assets/cameleer3-48.png';
+import cameleerLogo from '@cameleer/design-system/assets/cameleer3-logo.svg';
 
 function CameleerLogo() {
   return (