feat: Mail infinite scroll, remove sort header + pagination, connect filter/sort to MailList

frontend/src/pages/Mail.tsx

@@ -190,7 +190,8 @@ export function MailPage() {
         const result = await fetchMails(currentFolderId, mailsPage, sortBy, sortOrder);
         // Only update if still on the same folder
         if (selectedFolderIdRef.current === currentFolderId) {
-          setMails(result.mails);
+          // Append for infinite scroll (page > 1), replace on page 1 or folder change
+          setMails(mailsPage > 1 ? (prev) => [...prev, ...result.mails] : result.mails);
           setMailsTotal(result.total);
         }
       }
@@ -892,20 +893,15 @@ export function MailPage() {
             selectedMailId={selectedMail?.id || null}
             onSelectMail={handleSelectMail}
             loading={loadingMails}
-            currentPage={mailsPage}
-            total={mailsTotal}
-            pageSize={PAGE_SIZE}
-            onPageChange={setMailsPage}
             selectedMailIds={selectedMailIds}
             onToggleSelect={handleToggleSelect}
             onSelectAll={handleSelectAll}
-            sortBy={sortBy}
-            sortOrder={sortOrder}
-            onSortChange={(by, order) => {
-              setSortBy(by);
-              setSortOrder(order);
-              setMailsPage(1);
+            onLoadMore={() => {
+              if (mails.length < mailsTotal) {
+                setMailsPage((p) => p + 1);
+              }
             }}
+            hasMore={mails.length < mailsTotal}
           />
         </ResizablePanel>