feat(recipes): add recently opened sort with modal open tracking

Track recipe modal opens in a separate stats file (never touching recipe
JSON/EXIF), expose a fire-and-forget POST endpoint, and add an 'opened'
sort that hides never-opened recipes as a true recently-opened view.
Includes i18n for all locales and backend/frontend tests.

static/js/components/RecipeModal.js

@@ -306,6 +306,14 @@ class RecipeModal {
         modalManager.showModal('recipeModal');
 
         if (this.recipeId) {
+            // Fire-and-forget: record this open for the "Recently Opened"
+            // sort. Tracking must never disturb the modal, so failures are
+            // swallowed.
+            fetch(`/api/lm/recipe/${encodeURIComponent(this.recipeId)}/opened`, {
+                method: 'POST',
+                keepalive: true,
+            }).catch(() => {});
+
             const hydrationRequestId = ++this.recipeHydrationRequestId;
             const requestEditVersions = this.captureLocalEditVersions();
             this.hydrateRecipeDetails(

static/js/utils/MasonryScroller.js

@@ -646,10 +646,17 @@ export class MasonryScroller {
             const pageType = state.currentPageType;
 
             if (pageType === 'recipes') {
-                placeholderText = `
-                    <p>No recipes found</p>
-                    <p>Add recipe images to your recipes folder to see them here.</p>
-                `;
+                if (String(getCurrentPageState().sortBy).startsWith('opened')) {
+                    placeholderText = `
+                        <p>No recently opened recipes</p>
+                        <p>Recipes you open will appear here.</p>
+                    `;
+                } else {
+                    placeholderText = `
+                        <p>No recipes found</p>
+                        <p>Add recipe images to your recipes folder to see them here.</p>
+                    `;
+                }
             } else if (pageType === 'loras') {
                 placeholderText = `
                     <p>No LoRAs found</p>

static/js/utils/VirtualScroller.js

@@ -699,10 +699,17 @@ export class VirtualScroller {
             const pageType = state.currentPageType;
 
             if (pageType === 'recipes') {
-                placeholderText = `
-                    <p>No recipes found</p>
-                    <p>Add recipe images to your recipes folder to see them here.</p>
-                `;
+                if (String(getCurrentPageState().sortBy).startsWith('opened')) {
+                    placeholderText = `
+                        <p>No recently opened recipes</p>
+                        <p>Recipes you open will appear here.</p>
+                    `;
+                } else {
+                    placeholderText = `
+                        <p>No recipes found</p>
+                        <p>Add recipe images to your recipes folder to see them here.</p>
+                    `;
+                }
             } else if (pageType === 'loras') {
                 placeholderText = `
                     <p>No LoRAs found</p>