feat(planner): overhaul desktop layout — flip tiles, no right panel

Replaces 3-panel layout with 2-panel (sidebar + full-width grid):
- Remove persistent right panel and toolbar + Gericht hinzufügen button
- grid-cols-7 tiles use DesktopDayTile (CSS 3D card flip)
- RecipePickerDrawer slides in on tile CTA / Gericht tauschen
- Page-owned activeSlotId + drawerOpen/drawerSlotId state
- Single Escape handler: drawer > flip priority
- Extend server load to forward recipe tags from /v1/recipes API

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

frontend/src/lib/planner/RecipePickerDrawer.svelte

@@ -60,18 +60,20 @@
 		</button>
 	</div>
 
-	<!-- RecipePicker content -->
+	<!-- RecipePicker content — only mount when open to avoid duplicate text in DOM -->
 	<div style="overflow-y: auto; flex: 1;">
-		<RecipePicker
-			{planId}
-			date={slotDate}
-			dateLabel={slotDate}
-			{suggestions}
-			{allRecipes}
-			{isLoading}
-			{onpick}
-			{excludeRecipeId}
-			{replacingRecipe}
-		/>
+		{#if open}
+			<RecipePicker
+				{planId}
+				date={slotDate}
+				dateLabel={slotDate}
+				{suggestions}
+				{allRecipes}
+				{isLoading}
+				{onpick}
+				{excludeRecipeId}
+				{replacingRecipe}
+			/>
+		{/if}
 	</div>
 </div>