fix(compare): repair the mobile add-school modal

The 'add school' modal passed no title to Modal, so its header held only
the close button — shoved to the far left by justify-content:space-between
in an otherwise-empty bar — while the real title was rendered separately
inside the content. Pass the title to Modal so the header reads title
(left) + close (right), and drop the duplicate in-content heading.

Also: the mobile full-width result button targeted a dead .addButton
selector (the button never had that class), so it rendered inconsistently
— give the button a real module class and full width on mobile, tighten
the stacked cards, and give the bottom sheet a stable min-height so its
empty state isn't a tiny stub.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0146VHeLAWjDVE2B5uU67jCB

nextjs-app/components/SchoolSearchModal.tsx

@@ -81,10 +81,8 @@ export function SchoolSearchModal({ isOpen, onClose }: SchoolSearchModalProps) {
   };
 
   return (
-    <Modal isOpen={isOpen} onClose={handleClose}>
+    <Modal isOpen={isOpen} onClose={handleClose} title="Add School to Comparison">
       <div className={styles.modalContent}>
-        <h2 className={styles.title}>Add School to Comparison</h2>
-
         {!canAddMore && (
           <div className={styles.warning}>
             Maximum 5 schools can be compared. Remove a school to add another.
@@ -129,9 +127,9 @@ export function SchoolSearchModal({ isOpen, onClose }: SchoolSearchModalProps) {
                 <button
                   onClick={() => handleAddSchool(school)}
                   disabled={alreadySelected || !canAddMore}
-                  className={
+                  className={`${styles.resultButton} ${
                     alreadySelected ? "btn btn-active" : "btn btn-secondary"
-                  }
+                  }`}
                 >
                   {alreadySelected ? "✓ Comparing" : "+ Compare"}
                 </button>