Split Print into Save / Save & Print -- saving no longer requires also printing

Name is now required (it's the only thing identifying what got saved),
and printing is an explicit separate choice instead of an implicit
side-effect of naming something.

views/upload.erb

@@ -23,11 +23,12 @@
           </div>
           <div class="row g-2 align-items-end">
             <div class="col-auto">
-              <label for="save_as_zpl" class="form-label">Save as (optional)</label>
-              <input name="save_as" class="form-control" type="text" id="save_as_zpl" placeholder="label name" />
+              <label for="save_as_zpl" class="form-label">Name</label>
+              <input name="save_as" class="form-control" type="text" id="save_as_zpl" placeholder="label name" required />
             </div>
             <div class="col-auto">
-              <button class="btn btn-secondary" type="submit">Print</button>
+              <button class="btn btn-outline-secondary" type="submit" name="commit" value="save">Save</button>
+              <button class="btn btn-secondary" type="submit" name="commit" value="save_and_print">Save &amp; Print</button>
             </div>
           </div>
         </form>