Fix order saving, isMyOrder, blocked waiters, options pricing; add preferences, table groups, product images

Backend:
- OrderItemInput accepts option objects {id,name,price_delta} instead of int IDs
- extra_cost from selected options added to unit_price snapshot
- GET /api/products/?all=true for manager (includes unavailable)
- PUT /api/products/{id} now replaces options, ingredients, preference_sets
- POST /api/products/{id}/image — persistent image upload to /app/data/product_images
- New models: ProductPreferenceSet, ProductPreferenceChoice, TableGroup
- tables: group_id FK, hard delete (?hard=true), batch create POST /api/tables/batch
- GET /api/tables/groups + POST/PUT/DELETE groups endpoints
- POST /api/auth/me endpoint for token rehydration
- Auto-migration on startup for new columns

PWA:
- AuthRehydrator: fetches /auth/me on load so isMyOrder works after page reload
- 401 response force-logs out (covers blocked waiters)
- ItemOptionsModal: uses extra_cost correctly, shows preferences as radio buttons

Manager:
- ProductsPage: shows unavailable products greyed out, category color picker + reorder,
  full option/ingredient/preference editing, image upload
- TablesPage: table groups, auto-increment, deactivate vs hard delete, batch add

waiter_pwa/src/components/ItemOptionsModal.jsx

@@ -8,12 +8,21 @@ export default function ItemOptionsModal({ product, onAdd, onClose }) {
 
   const options = product.options || []
   const ingredients = product.ingredients || []
+  const preferenceSets = product.preference_sets || []
+
+  const [selectedPreferences, setSelectedPreferences] = useState(
+    Object.fromEntries(preferenceSets.map(ps => [ps.id, null]))
+  )
+
+  function selectPreference(setId, choice) {
+    setSelectedPreferences(prev => ({ ...prev, [setId]: choice }))
+  }
 
   function toggleOption(opt) {
     setSelectedOptions(prev => {
       const exists = prev.find(o => o.id === opt.id)
       if (exists) return prev.filter(o => o.id !== opt.id)
-      return [...prev, { id: opt.id, name: opt.name, price_delta: opt.price_delta }]
+      return [...prev, { id: opt.id, name: opt.name, price_delta: opt.extra_cost ?? 0 }]
     })
   }
 
@@ -23,11 +32,21 @@ export default function ItemOptionsModal({ product, onAdd, onClose }) {
     )
   }
 
-  const extraPrice = selectedOptions.reduce((s, o) => s + (o.price_delta || 0), 0)
+  const prefExtra = Object.values(selectedPreferences).reduce((s, ch) => s + (ch?.extra_cost ?? 0), 0)
+  const extraPrice = selectedOptions.reduce((s, o) => s + (o.price_delta ?? o.extra_cost ?? 0), 0) + prefExtra
   const totalPrice = (product.base_price + extraPrice) * quantity
 
   function handleAdd() {
-    onAdd({ product_id: product.id, quantity, selected_options: selectedOptions, removed_ingredients: removedIngredients, notes })
+    const prefChoices = Object.values(selectedPreferences)
+      .filter(Boolean)
+      .map(ch => ({ id: ch.id, name: ch.name, price_delta: ch.extra_cost ?? 0 }))
+    onAdd({
+      product_id: product.id,
+      quantity,
+      selected_options: [...selectedOptions, ...prefChoices],
+      removed_ingredients: removedIngredients,
+      notes,
+    })
     onClose()
   }
 
@@ -49,12 +68,30 @@ export default function ItemOptionsModal({ product, onAdd, onClose }) {
                   onChange={() => toggleOption(opt)}
                 />
                 <span>{opt.name}</span>
-                {opt.price_delta > 0 && <span className="option-price">+{Number(opt.price_delta).toFixed(2)} €</span>}
+                {(opt.extra_cost ?? 0) !== 0 && <span className="option-price">{(opt.extra_cost ?? 0) > 0 ? '+' : ''}{Number(opt.extra_cost).toFixed(2)} €</span>}
               </label>
             ))}
           </section>
         )}
 
+        {preferenceSets.map(ps => (
+          <section key={ps.id} className="modal-section">
+            <h3>{ps.name}</h3>
+            {ps.choices.map(ch => (
+              <label key={ch.id} className="modal-option">
+                <input
+                  type="radio"
+                  name={`pref-${ps.id}`}
+                  checked={selectedPreferences[ps.id]?.id === ch.id}
+                  onChange={() => selectPreference(ps.id, ch)}
+                />
+                <span>{ch.name}</span>
+                {(ch.extra_cost ?? 0) !== 0 && <span className="option-price">{(ch.extra_cost ?? 0) > 0 ? '+' : ''}{Number(ch.extra_cost).toFixed(2)} €</span>}
+              </label>
+            ))}
+          </section>
+        ))}
+
         {ingredients.length > 0 && (
           <section className="modal-section">
             <h3>Αφαίρεση υλικών</h3>