Fix more CSRFs (#8035)

Follow-up of #8000 

Some were still missed in `feedController`.
even had comments but no check:

https://github.com/FreshRSS/FreshRSS/blob/0d463b67bdade2e896b7fa74595950eeaadd55fe/app/Controllers/feedController.php#L1053-L1055

https://github.com/FreshRSS/FreshRSS/blob/0d463b67bdade2e896b7fa74595950eeaadd55fe/app/Controllers/feedController.php#L374-L376

app/Controllers/feedController.php

@@ -379,6 +379,9 @@ class FreshRSS_feed_Controller extends FreshRSS_ActionController {
 	 *   - id (default: false)
 	 */
 	public function truncateAction(): void {
+		if (!Minz_Request::isPost()) {
+			Minz_Request::forward(['c' => 'subscription'], true);
+		}
 		$id = Minz_Request::paramInt('id');
 		$url_redirect = [
 			'c' => 'subscription',
@@ -1059,6 +1062,9 @@ class FreshRSS_feed_Controller extends FreshRSS_ActionController {
 	 *   - id (default: false)
 	 */
 	public function deleteAction(): void {
+		if (!Minz_Request::isPost()) {
+			Minz_Request::forward(['c' => 'subscription'], true);
+		}
 		$from = Minz_Request::paramString('from');
 		$id = Minz_Request::paramInt('id');
 
@@ -1096,6 +1102,9 @@ class FreshRSS_feed_Controller extends FreshRSS_ActionController {
 	 *
 	 */
 	public function clearCacheAction(): void {
+		if (!Minz_Request::isPost()) {
+			Minz_Request::forward(['c' => 'subscription'], true);
+		}
 		//Get Feed.
 		$id = Minz_Request::paramInt('id');
 
@@ -1122,6 +1131,9 @@ class FreshRSS_feed_Controller extends FreshRSS_ActionController {
 	 * @throws FreshRSS_BadUrl_Exception
 	 */
 	public function reloadAction(): void {
+		if (!Minz_Request::isPost()) {
+			Minz_Request::forward(['c' => 'subscription'], true);
+		}
 		if (function_exists('set_time_limit')) {
 			@set_time_limit(300);
 		}

app/views/helpers/feed/update.phtml

@@ -870,9 +870,9 @@
 	<h2><?= _t('sub.feed.maintenance.title') ?></h2>
 	<div class="form-group">
 		<div class="group-controls">
-			<a class="btn btn-important" href="<?= _url('feed', 'clearCache', 'id', $this->feed->id(), '#', 'slider') ?>">
+			<button class="btn btn-important" form="post-csrf" formaction="<?= _url('feed', 'clearCache', 'id', $this->feed->id(), '#', 'slider') ?>">
 				<?= _t('sub.feed.maintenance.clear_cache') ?>
-			</a>
+			</button>
 			<p class="help"><?= _i('help') ?> <?= _t('sub.feed.maintenance.clear_cache_help') ?></p>
 		</div>
 		<div class="group-controls">