Initial commit: ZPL-native PDF printing, drop CUPS dependency

views/upload.erb

@@ -0,0 +1,11 @@
+        <form action="/upload" class="dropzone" id="upload-form" method="POST" enctype="multipart/form-data">
+          <div class="mb-3">
+            <label for="formFile" class="form-label">Upload .pdf or .zpl to print label</label>
+            <input name="file" class="form-control" type="file" id="formFile" accept=".pdf,.zpl" />
+          </div>
+          <button class="btn btn-secondary" type="submit">Upload</button>
+        </form>
+
+        <form action="/test-print" method="POST" class="mt-3">
+          <button class="btn btn-outline-secondary" type="submit">Print test label</button>
+        </form>