Add OrgAvatar component and frontend-utils package

- Create @reviq/frontend-utils package for frontend-specific utilities
- Add OrgAvatar component with size variants (xs, sm, md, lg, xl)
- Display org initials with deterministic colors when no logo available
- Add getOrgInitials and getOrgColor utility functions
- Update org-switcher and all org display pages to use OrgAvatar
- Add noNonNullAssertion lint rule as error in biome.jsonc

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

biome.jsonc

@@ -40,6 +40,13 @@
     "indentStyle": "space",
     "indentWidth": 2
   },
+  "linter": {
+    "rules": {
+      "style": {
+        "noNonNullAssertion": "error"
+      }
+    }
+  },
   "overrides": [
     {
       // Svelte 5 runes require `let` for $props(), template variables/imports appear unused to Biome,