Various improvements to pages: notifications and subscriptions

- fix rounding on /notifications/subscriptions
- add navigation interconnectivity between notifications and subscriptions
- use modern style for tabs
- clearing notificatons: hide the whole form instead of div. It doesn't seem like its changed via JS?
- replace issue-title-buttons and edit-buttons with universal top-right-buttons, get rid of tw-mr-0 helpers
- repo issues: fix misalignments on mobile view

web_src/css/base.css

@@ -246,6 +246,18 @@ h1.error-code {
   user-select: none;
 }
 
+.top-right-buttons {
+  gap: 0.5rem;
+}
+
+.top-right-buttons .ui.button {
+  margin-right: 0;
+}
+
+.ui.partial.secondary.menu {
+  margin-bottom: 0;
+}
+
 a {
   color: var(--color-primary);
   cursor: pointer;