feat(frontend): responsive design for mobile (RWD)

- Layout: mobile hamburger + drawer nav (backdrop button + sibling nav),
  desktop sidebar hidden on small screens, p-4 md:p-8 main padding
- Products: card list view on mobile, flex-wrap filters
- Lab results: card list view on mobile
- ProductForm: responsive grids (grid-cols-1 sm:grid-cols-2), skin
  profile checkboxes 2→3 cols, active ingredient row restructured
  (name+✕ in flex row, percent/strength/irritation in 3-col grid),
  section headers stack on mobile
- Skin snapshots: date+icons on one row, badges on separate row below
- Product [id] header: back link stacked above title, redundant badge removed
- Routines header: flex-col on mobile, sm:flex-row

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/routes/health/lab-results/+page.svelte

@@ -79,7 +79,7 @@
 		<Card>
 			<CardHeader><CardTitle>{m["labResults_newTitle"]()}</CardTitle></CardHeader>
 			<CardContent>
-				<form method="POST" action="?/create" use:enhance class="grid grid-cols-2 gap-4">
+				<form method="POST" action="?/create" use:enhance class="grid grid-cols-1 sm:grid-cols-2 gap-4">
 					<div class="space-y-1">
 						<Label for="collected_at">{m["labResults_date"]()}</Label>
 						<Input id="collected_at" name="collected_at" type="date" required />
@@ -125,7 +125,8 @@
 		</Card>
 	{/if}
 
-	<div class="rounded-md border border-border">
+	<!-- Desktop: table -->
+	<div class="hidden rounded-md border border-border md:block">
 		<Table>
 			<TableHeader>
 				<TableRow>
@@ -173,4 +174,34 @@
 			</TableBody>
 		</Table>
 	</div>
+
+	<!-- Mobile: cards -->
+	<div class="flex flex-col gap-3 md:hidden">
+		{#each data.results as r (r.record_id)}
+			<div class="rounded-lg border border-border p-4 flex flex-col gap-1">
+				<div class="flex items-start justify-between gap-2">
+					<span class="font-medium">{r.test_name_original ?? r.test_code}</span>
+					{#if r.flag}
+						<span class="shrink-0 rounded-full px-2 py-0.5 text-xs font-medium {flagColors[r.flag] ?? ''}">
+							{r.flag}
+						</span>
+					{/if}
+				</div>
+				<p class="text-sm text-muted-foreground">{r.collected_at.slice(0, 10)}</p>
+				<div class="flex items-center gap-2 text-sm">
+					<span class="font-mono text-xs text-muted-foreground">{r.test_code}</span>
+					{#if r.value_num != null}
+						<span>{r.value_num} {r.unit_original ?? ''}</span>
+					{:else if r.value_text}
+						<span>{r.value_text}</span>
+					{/if}
+				</div>
+				{#if r.lab}
+					<p class="text-xs text-muted-foreground">{r.lab}</p>
+				{/if}
+			</div>
+		{:else}
+			<p class="py-8 text-center text-sm text-muted-foreground">{m["labResults_noResults"]()}</p>
+		{/each}
+	</div>
 </div>