portability: replace M_PI / std::numbers::pi with a host+device-safe PI

M_PI is a POSIX <math.h> extension that MSVC does not define without
_USE_MATH_DEFINES. std::numbers::pi (introduced in the viewer guard commit) is
C++20, but CUDA here is compiled as C++17 (CMAKE_CUDA_STANDARD 17) and several
common/ headers are pulled into .cu device translation units, so std::numbers is
not available there.

Add common/JFJochMath.h with a dependency-free `constexpr double PI` that works
in host code (including MSVC), in CUDA device code, and under C++17/20, and use
it everywhere:
- common/ and image_analysis/ (incl. CUDA .cu): 78 M_PI occurrences, 22 files
- broker/OpenAPIConvert.cpp
- viewer/: the 5 files that used std::numbers::pi now use PI, for one consistent
  convention across the codebase

Verified to build: JFJochImageAnalysis (incl. CUDA), jfjoch_viewer, JFJochBroker.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

common/GoniometerAxis.cpp

@@ -1,6 +1,7 @@
 // SPDX-FileCopyrightText: 2025 Filip Leonarski, Paul Scherrer Institute <filip.leonarski@psi.ch>
 // SPDX-License-Identifier: GPL-3.0-only
 
+#include "JFJochMath.h"
 #include <cmath>
 #include <algorithm>
 
@@ -138,6 +139,6 @@ std::vector<double> GoniometerAxis::GetAngleContainerEnd(int64_t max_image_numbe
 }
 
 RotMatrix GoniometerAxis::GetTransformationAngle(float angle_deg) const {
-    auto angle_rad = angle_deg / 180.0f * static_cast<float>(M_PI);
+    auto angle_rad = angle_deg / 180.0f * static_cast<float>(PI);
     return {angle_rad, axis};
 }