fix(lighthouse): use warn for preset audit assertions + add robots.txt

Per CTO guidance, override preset per-audit assertions to warn:
- errors-in-console: warn (browser dev errors, not prod blockers)
- network-dependency-tree-insight: warn (existing perf debt)
- robots-txt: warn (existing SEO gap)
- unused-javascript: warn (existing perf debt)

Add public/robots.txt so the robots-txt audit passes at warn level.
These are known gaps to address post-merge, not merge blockers.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

lighthouserc.json

@@ -11,7 +11,11 @@
         "categories:performance": ["warn", { "minScore": 0.5 }],
         "categories:accessibility": ["error", { "minScore": 0.7 }],
         "categories:best-practices": ["warn", { "minScore": 0.8 }],
-        "categories:seo": ["warn", { "minScore": 0.7 }]
+        "categories:seo": ["warn", { "minScore": 0.7 }],
+        "errors-in-console": ["warn"],
+        "network-dependency-tree-insight": ["warn"],
+        "robots-txt": ["warn"],
+        "unused-javascript": ["warn"]
       }
     },
     "upload": {

public/robots.txt

@@ -0,0 +1,4 @@
+User-agent: *
+Allow: /
+
+Sitemap: https://cartsnitch.com/sitemap.xml