chore(dist): add placeholder favicon, gitignore unused icons.svg

- favicon.svg: CF lightning bolt as favicon placeholder until Robin
  bird icon is designed; wired into index.html <link rel=icon>
- icons.svg: leftover social media sprite sheet from old Vue setup,
  added to .gitignore (not referenced by the static UI)

.gitignore

@@ -11,6 +11,8 @@ node_modules
 # dist/ was previously generated by Vite; now it holds the static UI (dist/index.html).
 # Ignore generated assets but track the hand-crafted index.html.
 dist/assets/
+# Social icon sprite sheet leftover from old Vue setup — not used by the static UI
+dist/icons.svg
 dist-ssr
 *.local
 

dist/index.html

@@ -4,6 +4,8 @@
   <meta charset="UTF-8" />
   <meta name="viewport" content="width=device-width, initial-scale=1.0" />
   <title>Robin</title>
+  <!-- Placeholder favicon — replace with Robin bird icon once designed -->
+  <link rel="icon" href="favicon.svg" type="image/svg+xml" />
   <style>
     :root {
       --bg:        #0f172a;