[server] add cql2 filtering

[jef-n]

Add server support for filtering using qgis and cql2 expressions

AI (local Qwen 3.5) helped creating the tests.

[github-actions]

🪟 x64-windows — ❌ 1 port(s) failed

Failed: lapack-reference

📦 lapack-reference

_{from stdout-x64-windows-release.log}

CMake Error at scripts/cmake/vcpkg_execute_required_process.cmake:127 (message):
    Command failed: C:\\.vcpkg\\downloads\\tools\\ninja-1.13.2-windows\\ninja.exe -v
    Working Directory: C:/src/lapack-reference/x64-windows-release-rel/vcpkg-parallel-configure
    Error code: 1
    See logs for more information:
      C:\src\lapack-reference\config-x64-windows-release-rel-CMakeCache.txt.log
      C:\src\lapack-reference\config-x64-windows-release-rel-CMakeConfigureLog.yaml.log
      C:\src\lapack-reference\config-x64-windows-release-out.log

_{from config-x64-windows-release-rel-CMakeCache.txt.log (key errors)}

//Error when cmake_install.cmake encounters absolute INSTALL DESTINATION.
//Deprecated.  Use -W[no-]error=deprecated instead.

📦 Download failing-port-logs-x64-windows artifact · 📑 Download full build-logs-x64-windows artifact · 🔧 Workflow run · 📌 Commit 428f778

🍎 MacOS Qt6 builds

Download MacOS Qt6 builds of this PR for testing.
This app is not notarized, run sudo xattr -d com.apple.quarantine /Applications/QGIS*.app to avoid the warning
(Built from commit 1c3654c)

🪟 Windows Qt6 builds

Download Windows Qt6 builds of this PR for testing.
To execute locally, unzip the downloaded zip file and run bin\qgis-bin.exe in the extracted directory.
You might be prompted by Windows Defender click "Run anyway"
(Built from commit 1c3654c)

[elpaso]

LGTM, nice improvement!