feat(stellungnahme): E-Mail-Button immer zeigen (leerer Empfänger = an sich selbst)

src/lib/components/blocks/StellingnahmeGeneratorBlock.svelte

@@ -225,9 +225,10 @@ Karl-Liebknecht-Straße 4
   );
 
   const mailtoLink = $derived.by(() => {
-    if (!block.recipientEmail || !outputText) return "";
+    if (!outputText) return "";
     const subject = `Einwendung Regionalplan Südwestthüringen – Vorranggebiet ${gebietsBez}`;
-    return `mailto:${block.recipientEmail}?subject=${encodeURIComponent(subject)}&body=${encodeURIComponent(outputText)}`;
+    const to = block.recipientEmail ?? "";
+    return `mailto:${to}?subject=${encodeURIComponent(subject)}&body=${encodeURIComponent(outputText)}`;
   });
 
   function buildText(): string {
@@ -920,7 +921,7 @@ ${"=".repeat(64)}`;
               <button class="rounded-md border border-stein-300 px-3 py-1.5 text-xs font-medium text-stein-700 hover:bg-stein-50" onclick={copyText}>{copyFeedback || "Kopieren"}</button>
               <button class="rounded-md border border-stein-300 px-3 py-1.5 text-xs font-medium text-stein-700 hover:bg-stein-50" onclick={downloadText}>Herunterladen</button>
               <button class="rounded-md border border-stein-300 px-3 py-1.5 text-xs font-medium text-stein-700 hover:bg-stein-50" onclick={printText}>Drucken</button>
-              {#if mailtoLink}
+              {#if mailtoLink}
                 <a href={mailtoLink} class="rounded-md border border-wald-400 bg-wald-50 px-3 py-1.5 text-xs font-medium text-wald-700 hover:bg-wald-100">{block.recipientEmail ? "Per E-Mail senden" : "Per E-Mail (an mich)"}</a>
               {/if}
             </div>