UX: Formular-Buttons in Modal-Footer + Kalender-Icons amber

- Alle Formular-Buttons (health, praxen, diary, dog-profile, poison)
  aus dem scrollbaren Body in den festen Modal-Footer verschoben
  (form="form-id" Attribut, btn-Suche via document.querySelector)
- Kalender-Icon Filter korrigiert: brightness(0)+invert(0.55) vermeidet
  Channel-Clipping bei sepia auf Weiß → ergibt echtes Amber (~#C4843A)
- SW-Cache: by-v18 → by-v19

backend/static/js/pages/diary.js

@@ -417,16 +417,17 @@ window.Page_diary = (() => {
                object-fit:cover;border-radius:var(--radius-md);margin-top:var(--space-2)">
         </div>
         ` : ''}
-        <div style="display:flex;gap:var(--space-2);margin-top:var(--space-4)">
-          <button type="button" class="btn btn-secondary flex-1" id="diary-form-cancel">Abbrechen</button>
-          <button type="submit" class="btn btn-primary flex-1">
-            ${isEdit ? 'Speichern' : 'Erstellen'}
-          </button>
-        </div>
       </form>
     `;
 
-    UI.modal.open({ title: isEdit ? 'Eintrag bearbeiten' : 'Neuer Eintrag', body });
+    const footer = `
+      <button type="button" class="btn btn-secondary flex-1" id="diary-form-cancel">Abbrechen</button>
+      <button type="submit" form="diary-form" class="btn btn-primary flex-1">
+        ${isEdit ? 'Speichern' : 'Erstellen'}
+      </button>
+    `;
+
+    UI.modal.open({ title: isEdit ? 'Eintrag bearbeiten' : 'Neuer Eintrag', body, footer });
 
     const form = document.getElementById('diary-form');
 
@@ -454,7 +455,7 @@ window.Page_diary = (() => {
 
     form.addEventListener('submit', async e => {
       e.preventDefault();
-      const submitBtn = form.querySelector('[type="submit"]');
+      const submitBtn = document.querySelector('[form="diary-form"][type="submit"]') || form.querySelector('[type="submit"]');
       const fd = UI.formData(form);
 
       // dog_ids zusammenbauen: aktiver Hund + gewählte weitere