feat(forms): add inline blur validation for name and email

app/pages/join.vue

@@ -128,7 +128,10 @@
                   class="form-input"
                   type="text"
                   required
+                  @blur="validateName"
+                  @input="if (fieldErrors.name) fieldErrors.name = ''"
                 >
+                <p v-if="fieldErrors.name" class="field-error">{{ fieldErrors.name }}</p>
               </div>
               <div class="form-group">
                 <label class="form-label" for="join-email">Email</label>
@@ -139,7 +142,10 @@
                   type="email"
                   placeholder="you@example.com"
                   required
+                  @blur="validateEmail"
+                  @input="if (fieldErrors.email) fieldErrors.email = ''"
                 >
+                <p v-if="fieldErrors.email" class="field-error">{{ fieldErrors.email }}</p>
               </div>
               <div class="form-group">
                 <label class="form-label">Circle</label>
@@ -346,6 +352,23 @@ const errorMessage = ref("");
 const successMessage = ref("");
 const cadence = ref("monthly"); // 'monthly' | 'annual'
 
+// Inline blur validation (UI feedback only — does not block submission)
+const fieldErrors = reactive({ name: "", email: "" });
+
+const validateName = () => {
+  fieldErrors.name = form.name.trim() ? "" : "Please enter your name.";
+};
+
+const validateEmail = () => {
+  const value = form.email.trim();
+  if (!value) {
+    fieldErrors.email = "";
+    return;
+  }
+  const ok = /^[^\s@]+@[^\s@]+\.[^\s@]+$/.test(value);
+  fieldErrors.email = ok ? "" : "Please enter a valid email address.";
+};
+
 // Flow overlay state — drives the post-submit full-viewport UI.
 // 'idle' = overlay hidden; user is editing the form.
 // 'creating-customer' | 'opening-payment' | 'processing-payment'
@@ -762,6 +785,11 @@ onUnmounted(() => {
 .form-input::placeholder {
   color: var(--text-faint);
 }
+.field-error {
+  font-size: 11px;
+  color: var(--ember);
+  margin-top: 4px;
+}
 
 /* ---- CIRCLE RADIOS ---- */
 .circle-radios {