chore: auto-fix Biome formatting and configure lint rules

Run biome check --write --unsafe to fix tabs, import ordering, and
non-null assertions across entire codebase. Disable a11y rules not
applicable to this single-user app. Exclude auto-generated routeTree.

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

src/client/lib/formatters.ts

@@ -1,9 +1,9 @@
 export function formatWeight(grams: number | null | undefined): string {
-  if (grams == null) return "--";
-  return `${Math.round(grams)}g`;
+	if (grams == null) return "--";
+	return `${Math.round(grams)}g`;
 }
 
 export function formatPrice(cents: number | null | undefined): string {
-  if (cents == null) return "--";
-  return `$${(cents / 100).toFixed(2)}`;
+	if (cents == null) return "--";
+	return `$${(cents / 100).toFixed(2)}`;
 }