feat: contact page improvements, Yandex map from addresses

- Instagram field: @username input with API validation (like team page)
- Phone validation: blocks auto-save when incomplete, shows warning
- SectionEditor: validate prop to conditionally block saves
- Yandex Map: auto-generated from addresses via Nominatim geocoding,
  dark theme, no API key needed
- Schedule: address hint linking to Contacts
- Renamed "Всплывающие окна" → "Формы записи", moved after Записи

src/app/admin/schedule/page.tsx

@@ -952,13 +952,18 @@ function CalendarGrid({
           value={location.name}
           onChange={(v) => onChange({ ...location, name: v })}
         />
-        <SelectField
-          label="Адрес"
-          value={location.address}
-          onChange={(v) => onChange({ ...location, address: v })}
-          options={addresses.map((a) => ({ value: a, label: a }))}
-          placeholder="Выберите адрес"
-        />
+        <div>
+          <SelectField
+            label="Адрес"
+            value={location.address}
+            onChange={(v) => onChange({ ...location, address: v })}
+            options={addresses.map((a) => ({ value: a, label: a }))}
+            placeholder="Выберите адрес"
+          />
+          <p className="mt-1 text-xs text-neutral-500">
+            Адреса задаются в <a href="/admin/contact" className="text-gold hover:text-gold-light transition-colors">Контактах</a>
+          </p>
+        </div>
       </div>
 
       {/* Calendar */}