Add shopping list tab with auto-generation from planner

- New ShoppingList.js view with category-grouped items
- Check item = auto-transfer to pantry
- "Generate shortfalls" button computes weekly needs vs pantry stock
- Badge on shopping tab icon shows unchecked item count
- Bottom dock expanded to 5 columns for new tab

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

index.html

@@ -465,10 +465,10 @@
         #app-bottom-nav .bottom-dock {
             position: relative;
             box-sizing: border-box;
-            width: min(calc(100% - 3.6rem), 20.9rem);
+            width: min(calc(100% - 2.4rem), 24.5rem);
             height: 3.34rem;
             display: grid;
-            grid-template-columns: repeat(4, minmax(0, 1fr));
+            grid-template-columns: repeat(5, minmax(0, 1fr));
             align-items: stretch;
             gap: 0.06rem;
             padding: 0.22rem;
@@ -547,7 +547,7 @@
                 padding-inline: 0.7rem;
             }
             #app-bottom-nav .bottom-dock {
-                width: min(calc(100% - 2.4rem), 19.7rem);
+                width: min(calc(100% - 1.6rem), 22.5rem);
                 height: 3.12rem;
                 gap: 0.05rem;
                 padding: 0.2rem;