Fix date decoration lines, remove post card hover border, use filled nav icons

- Remove ::before/::after decorative horizontal lines on post date
- Remove blue inset box-shadow from post card hover state
- Switch nav icons from outline (-o) to filled variants

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

static/css/page-spacing.css

@@ -70,4 +70,10 @@ a.image.fit {
         margin-top: 0.75rem;
         margin-bottom: 1rem;
     }
+}
+
+/* Убираем декоративные линии по бокам даты в заголовке поста */
+.post header.major .date::before,
+.post header.major .date::after {
+    display: none !important;
 }