fix: new clang-tidy errors

[bjsowa]

Public API Changes
None

[Copilot]

Pull request overview

This PR aims to resolve new clang-tidy/CI build issues by adjusting build configuration, CI dependencies, and clang-tidy settings across the web_video_server package.

Changes:

• Remove unused <cstring> includes flagged by clang-tidy include-cleaner.
• Update CI (rolling) to install libstdc++-16-dev to prevent clang-tidy header lookup failures.
• Adjust build/lint configuration: bump cmake_minimum_required(), remove the default C++14 fallback, and tweak .clang-tidy checks/options.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/web_video_server.cpp	Removes an unused <cstring> include.
src/streamers/vp9_streamer.cpp	Removes an unused <cstring> include.
src/streamers/vp8_streamer.cpp	Removes an unused <cstring> include.
src/streamers/png_streamers.cpp	Removes an unused <cstring> include.
src/streamers/jpeg_streamers.cpp	Removes an unused <cstring> include.
src/streamers/image_transport_streamer.cpp	Adds missing rclcpp/qos.hpp include for QoS-related types.
CMakeLists.txt	Raises minimum CMake version and removes the default CMAKE_CXX_STANDARD fallback.
.github/workflows/ci.yml	Installs libstdc++-16-dev on rolling to keep clang-tidy working.
.clang-tidy	Updates checks configuration and string quoting; adds a comment for a disabled check.

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