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/conftest.py

@@ -0,0 +1,59 @@
+import io
+import tempfile
+
+import pypdf
+import pytest
+
+from app import app as flask_app, get_pdf_page_count
+
+
+@pytest.fixture
+def app():
+    flask_app.config["TESTING"] = True
+    flask_app.config["UPLOAD_FOLDER"] = tempfile.mkdtemp()
+    flask_app.config["SECRET_KEY"] = "test-secret"
+    yield flask_app
+
+
+@pytest.fixture
+def client(app):
+    return app.test_client()
+
+
+def _make_pdf(num_pages=3):
+    writer = pypdf.PdfWriter()
+    for _ in range(num_pages):
+        writer.add_blank_page(width=612, height=792)
+    buf = io.BytesIO()
+    writer.write(buf)
+    buf.seek(0)
+    return buf
+
+
+@pytest.fixture
+def sample_pdf():
+    return _make_pdf(3).read()
+
+
+@pytest.fixture
+def large_pdf():
+    return _make_pdf(15).read()
+
+
+@pytest.fixture
+def corrupt_file():
+    return b"This is not a PDF at all"
+
+
+@pytest.fixture
+def sample_pdf_path(tmp_path):
+    path = tmp_path / "test.pdf"
+    path.write_bytes(_make_pdf(3).read())
+    return str(path)
+
+
+@pytest.fixture
+def corrupt_file_path(tmp_path):
+    path = tmp_path / "corrupt.pdf"
+    path.write_bytes(b"not a pdf")
+    return str(path)