port print-web-form app to nested flask structure

Replace stub print/ app with full PDF web print service from
~/print-web-form. Adapt UPLOAD_FOLDER to use Path(__file__).parent,
add pypdf dependency, port all tests (10 passing), remove unused static/.

print/tests/test_pdf_utils.py

@@ -0,0 +1,13 @@
+from app import get_pdf_page_count
+
+
+def test_page_count_valid_pdf(sample_pdf_path):
+    assert get_pdf_page_count(sample_pdf_path) == 3
+
+
+def test_page_count_corrupt_file(corrupt_file_path):
+    assert get_pdf_page_count(corrupt_file_path) is None
+
+
+def test_page_count_nonexistent_file():
+    assert get_pdf_page_count("/nonexistent/file.pdf") is None