feat(calendar-compact): polish + global not-prose opt-out support

CalendarCompact:
- denser layout (smaller padding/font/badge), header icon size-8
- icon stein-900 (black), subtle wald gradient background
- rounded-sm to match design tokens (was rounded-lg)
- list items link to linkTo + "#event-<slug>" anchor; <svelte:element>
  falls back to div when no linkTo is set
- not-prose on root so global content margins/list/link rules don't
  apply to the card subtree

blog-utils.resolveCalendarBlocks:
- when items array is empty, fall back to the full calendar_item pool
  (both default and compact variant get this) — saves editors from
  re-listing items on every page.

app.css: add `:where(:not(.not-prose *))` to .content p/h1-h4,
main a (link colour + underline), main ul/ol so subtrees marked
not-prose stop inheriting the global prose-like defaults.

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

src/app.css

@@ -304,13 +304,15 @@ h4 {
     }
 }
 
-/* Content-Links: Himmel (Design System – Links) */
-main a:not(.no-underline):not([class*="btn"]) {
+/* Content-Links: Himmel (Design System – Links).
+ * `:where(:not(.not-prose *))` schließt jeden Subtree mit `.not-prose`
+ * aus — Card-Links etc. behalten ihre eigene Farbe + kein Underline. */
+main a:not(.no-underline):not([class*="btn"]):where(:not(.not-prose *)) {
     color: var(--color-link);
     text-decoration: underline;
 }
 
-main a:not(.no-underline):not([class*="btn"]):hover {
+main a:not(.no-underline):not([class*="btn"]):where(:not(.not-prose *)):hover {
     color: var(--color-himmel-600);
 }
 
@@ -327,21 +329,21 @@ main strong {
     font-weight: 600;
 }
 
-main ul:not(.not-prose) {
+main ul:not(.not-prose):where(:not(.not-prose *)) {
     margin-left: 1em;
     margin-bottom: 1em;
 }
 
-main ul:not(.not-prose) li {
+main ul:not(.not-prose):where(:not(.not-prose *)) li {
     list-style: disc;
 }
 
-main ol:not(.not-prose) {
+main ol:not(.not-prose):where(:not(.not-prose *)) {
     margin-left: 1.1em;
     margin-bottom: 1em;
 }
 
-main ol:not(.not-prose) li {
+main ol:not(.not-prose):where(:not(.not-prose *)) li {
     list-style-type: decimal;
 }
 
@@ -473,15 +475,17 @@ article [data-block-type="markdown"] .markdown > p:first-child {
     max-width: 50%;
 }
 
-/* Content-Blöcke */
-.content p {
+/* Content-Blöcke. `:where(:not(.not-prose *))` lässt jeden Subtree mit
+ * .not-prose komplett ausserhalb dieser Margin-Defaults — Components, die
+ * eigene Abstände setzen, müssen nur `not-prose` auf den Root packen. */
+.content p:where(:not(.not-prose *)) {
     @apply mb-4;
 }
 
-.content h1,
-.content h2,
-.content h3,
-.content h4 {
+.content h1:where(:not(.not-prose *)),
+.content h2:where(:not(.not-prose *)),
+.content h3:where(:not(.not-prose *)),
+.content h4:where(:not(.not-prose *)) {
     @apply mb-2;
 }