Add multi-announcement management system

- Update inc/announcements.php to support listing, fetching by ID, toggling, and deleting multiple announcements
- Upgrade admin/index.php to an announcement management view with data table, status indicators, and create/edit sub-views
- Add admin table and action styles to styles.css without using inline style blocks
- Update index.php to render all currently active banner and hours announcements dynamically

inc/announcements.php

@@ -5,7 +5,7 @@
 
 require_once __DIR__ . '/db.php';
 
-function get_active_announcement(): ?array {
+function get_active_announcements(): array {
     $pdo = get_db();
     $today = date('Y-m-d');
 
@@ -15,7 +15,6 @@ function get_active_announcement(): ?array {
           AND (start_date IS NULL OR start_date = '' OR start_date <= :today1)
           AND (end_date IS NULL OR end_date = '' OR end_date >= :today2)
         ORDER BY id DESC
-        LIMIT 1
     ";
 
     $stmt = $pdo->prepare($sql);
@@ -23,15 +22,38 @@ function get_active_announcement(): ?array {
         ':today1' => $today,
         ':today2' => $today
     ]);
-    $result = $stmt->fetch();
+    return $stmt->fetchAll() ?: [];
+}
 
-    return $result ?: null;
+function get_active_announcement(): ?array {
+    $all = get_active_announcements();
+    return !empty($all) ? $all[0] : null;
 }
 
 function get_all_announcements(): array {
     $pdo = get_db();
     $stmt = $pdo->query("SELECT * FROM announcements ORDER BY id DESC");
-    return $stmt->fetchAll();
+    return $stmt->fetchAll() ?: [];
+}
+
+function get_announcement_by_id(int $id): ?array {
+    $pdo = get_db();
+    $stmt = $pdo->prepare("SELECT * FROM announcements WHERE id = ?");
+    $stmt->execute([$id]);
+    $item = $stmt->fetch();
+    return $item ?: null;
+}
+
+function delete_announcement(int $id): bool {
+    $pdo = get_db();
+    $stmt = $pdo->prepare("DELETE FROM announcements WHERE id = ?");
+    return $stmt->execute([$id]);
+}
+
+function toggle_announcement_active(int $id): bool {
+    $pdo = get_db();
+    $stmt = $pdo->prepare("UPDATE announcements SET is_active = CASE WHEN is_active = 1 THEN 0 ELSE 1 END, updated_at = CURRENT_TIMESTAMP WHERE id = ?");
+    return $stmt->execute([$id]);
 }
 
 function save_announcement(array $data, ?int $id = null): int {
@@ -46,7 +68,7 @@ function save_announcement(array $data, ?int $id = null): int {
     $showBanner = !empty($data['show_banner']) ? 1 : 0;
     $showInHours = !empty($data['show_in_hours']) ? 1 : 0;
 
-    if ($id) {
+    if ($id && $id > 0) {
         $stmt = $pdo->prepare("
             UPDATE announcements SET
                 is_active = ?,