show error if not valid amount

can't actually prevent the input to deny letters

lnbits/core/templates/core/wallet.html

@@ -330,6 +330,7 @@
                 :min="receive.minMax[0]"
                 :max="receive.minMax[1]"
                 :readonly="receive.lnurl && receive.lnurl.fixed"
+                inputmode="numeric"
               ></q-input>
             </q-card-section>
             <q-separator></q-separator>
@@ -355,6 +356,8 @@
                   :min="receive.minMax[0]"
                   :max="receive.minMax[1]"
                   :readonly="receive.lnurl && receive.lnurl.fixed"
+                  error-message="Not a valid amount"
+                  :error="!isValid"
                 >
                 </q-input>
                 <div class="col-2 self-end">

lnbits/static/js/wallet.js

@@ -97,6 +97,17 @@ window.WalletPageLogic = {
         .formatCurrency(0, this.receive.unit)
         .replace(/[\d.\s]/g, '')
         .trim()
+    },
+    isValid() {
+      if (!this.receive.data.amount) return true
+      return (
+        this.receive.data.amount >= this.receive.minMax[0] &&
+        this.receive.data.amount <= this.receive.minMax[1] &&
+        !isNaN(this.receive.data.amount) &&
+        this.receive.data.amount > 0 &&
+        !isNaN(parseFloat(this.receive.data.amount)) &&
+        /^\d*\.?\d*$/.test(this.receive.data.amount)
+      )
     }
   },
   methods: {