feat: add email field to business wizard, update success message

- Add email input field after textareas, before checkboxes
- Email required via both HTML 'required' attribute and JS validation
- POST email field to webhook as 'email' key
- Add .biz-field input[type='email'] CSS (inline + external) matching textarea style
- Update success message: 'We will email you the report once it is ready. AI generation typically takes 1-2 minutes.'
- Remove reference to new window / auto-download (no longer opens window)

style.css

@@ -792,6 +792,24 @@ img { max-width: 100%; height: auto; vertical-align: middle; }
   background: rgba(255,255,255,0.08);
 }
 .biz-field textarea::placeholder { color: rgba(255,255,255,0.3); }
+.biz-field input[type="email"] {
+  width: 100%;
+  padding: 0.8rem 1rem;
+  border-radius: var(--radius);
+  border: 1px solid var(--line-brass);
+  background: rgba(255,255,255,0.05);
+  color: #fff;
+  font-family: Inter, sans-serif;
+  font-size: 0.88rem;
+  outline: none;
+  transition: border-color 0.2s, background 0.2s;
+  box-sizing: border-box;
+}
+.biz-field input[type="email"]:focus {
+  border-color: var(--brass);
+  background: rgba(255,255,255,0.08);
+}
+.biz-field input[type="email"]::placeholder { color: rgba(255,255,255,0.3); }
 .biz-form .btn-lg { margin-top: 0.5rem; width: 100%; }
 .biz-checkbox-group {
   display: flex;