refactor(consolidate): IconButton + Badge-solid + @layer base + Massen-Migration

E: app.css Base-h1–h6 in @layer base → text-*!-Hacks in Titeln entfernt.
Neue Atoms: IconButton (runde Icon-Buttons), Badge solid-Variante + uppercase.

Migrationen (6 parallele Pässe):
- IconButton: 19 runde Nav/Close-Buttons (Carousel, Galleries, QuoteCarousel,
  PostOverview, Organisations, ImageModal).
- Badge: Kategorie/Status-Pills (PostCard, BlogOverview, kalender, Comments,
  CalendarBlock, FilesBlock, SearchableText, Stellingnahme).
- ui-Atome: Formular-Inputs (Comments, termin-melden, Stellingnahme) → TextInput/
  Textarea/Checkbox/SearchField; dunkle NewsletterInline bewusst raw.
- Button-Atom: ~20 inline Buttons in StellingnahmeGeneratorBlock.
- Radius-Sweep: Cards→rounded-lg (viele via .card-surface), Buttons/Inputs→rounded-md,
  Chips→rounded-full; StrommixBlock/Calendar/Files/Adressbuch u.a.

svelte-check 0 errors, voller Prod-Build grün.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/lib/components/blocks/CalendarCompactBlock.svelte

@@ -91,11 +91,11 @@
   </div>
 
   {#if upcoming.length === 0}
-    <p class="rounded-sm border border-stein-200 px-3 py-6 text-center text-sm text-stein-500">
+    <p class="rounded-lg border border-stein-200 px-3 py-6 text-center text-sm text-stein-500">
       {t(T.calendar_no_future_events)}
     </p>
   {:else}
-    <ul class="divide-y divide-stein-100 overflow-hidden rounded-sm border border-stein-200 bg-white">
+    <ul class="divide-y divide-stein-100 overflow-hidden rounded-lg border border-stein-200 bg-white">
       {#each upcoming as { it, start } (it._slug ?? it.title)}
         {@const timeStr = fmtTime(start)}
         {@const loc = locationText(it)}