feat: extend PWA offline support to all recipe routes and glaube pages

- Add offline support for category, tag, icon list pages
- Add offline support for favorites page (stores locally for offline)
- Add offline support for season list page
- Cache root page and glaube pages for offline access
- Dynamically discover glaube routes at build time using Vite glob
- Add db functions for getAllCategories, getAllTags, getAllIcons
- Pre-cache __data.json for all category, tag, icon, season subroutes
- Update service worker to cache glaube and root page responses

src/routes/[recipeLang=recipeLang]/icon/+page.ts

@@ -1,10 +1,40 @@
 import type { PageLoad } from "./$types";
+import { browser } from '$app/environment';
+import { isOffline, canUseOfflineData } from '$lib/offline/helpers';
+import { getAllIcons, isOfflineDataAvailable } from '$lib/offline/db';
 
-export async function load({ fetch }) {
-    let current_month = new Date().getMonth() + 1
-    const res_icons = await fetch(`/api/rezepte/items/icon`);
-    const item = await res_icons.json();
-    return {
-	    icons: item,
-    };
+export const load: PageLoad = async ({ fetch }) => {
+    // Check if we should use offline data
+    if (browser && isOffline() && canUseOfflineData()) {
+        try {
+            const hasOfflineData = await isOfflineDataAvailable();
+            if (hasOfflineData) {
+                const icons = await getAllIcons();
+                return { icons, isOffline: true };
+            }
+        } catch (error) {
+            console.error('Failed to load offline icons:', error);
+        }
+    }
+
+    // Online mode - fetch from API
+    try {
+        const res_icons = await fetch(`/api/rezepte/items/icon`);
+        const icons = await res_icons.json();
+        return { icons, isOffline: false };
+    } catch (error) {
+        // Network error - try offline fallback
+        if (browser && canUseOfflineData()) {
+            try {
+                const hasOfflineData = await isOfflineDataAvailable();
+                if (hasOfflineData) {
+                    const icons = await getAllIcons();
+                    return { icons, isOffline: true };
+                }
+            } catch (offlineError) {
+                console.error('Failed to load offline icons:', offlineError);
+            }
+        }
+        throw error;
+    }
 };