UX: fix cakeday & user directory containers (#109)

Before:


![image](https://github.com/user-attachments/assets/dbc14156-2def-42c1-bbc4-b2366a9b89fa)


![image](https://github.com/user-attachments/assets/92554725-ce2d-4756-9f9e-e49b91f0c227)


After:


![image](https://github.com/user-attachments/assets/a2c90617-6efa-4bdb-8149-cd7d5cea6e95)


![image](https://github.com/user-attachments/assets/2188f0be-58ef-4996-8628-57705cc6d52c)

scss/main.scss

@@ -78,11 +78,13 @@ body:not(.has-full-page-chat) {
       .body-page,
       .topic-above-footer-buttons-outlet .presence-users,
       .global-notice,
+      .users-directory.directory,
       .container .user-main,
       .container.groups-index,
       .container.badges,
       .container.tags-index,
-      .container.group {
+      .container.group,
+      .container.cakeday {
         @include breakpoint(medium, $rule: min-width) {
           max-width: 1000px;
           margin-inline: auto;

scss/misc.scss

@@ -98,3 +98,7 @@ input[type="color"]:focus,
 .group-details-container {
   border-radius: var(--d-border-radius);
 }
+
+.period-chooser-header {
+  border-radius: 0;
+}