fix: build x264 from source in rpm-builder to resolve x264-sys bindgen failure on Fedora

[Copilot]

RPMFusion's x264-devel package produces headers where bindgen generates x264_param_t as an opaque 1-byte placeholder instead of the full struct, causing a compile-time size assertion overflow (1_usize - 1024_usize) in x264-sys 0.2.x during the Fedora RPM build.

Changes

• docker/Dockerfile.packages (rpm-builder stage)
  • Removed x264-devel from the dnf install list
  • Added a step to clone x264 from VideoLAN's stable branch and build/install from source (--enable-shared --disable-cli --prefix=/usr --libdir=/usr/lib64), which exposes a fully-defined x264_param_t that satisfies the x264-sys size assertions

RUN git clone --depth 1 https://code.videolan.org/videolan/x264.git /tmp/x264 \
    && cd /tmp/x264 \
    && ./configure --enable-shared --disable-cli --prefix=/usr --libdir=/usr/lib64 \
    && make -j"$(nproc)" install \
    && ldconfig \
    && rm -rf /tmp/x264

The VideoLAN source with default configure flags produces headers where x264_param_t is fully defined, so bindgen generates a complete Rust struct and the size_of assertion resolves correctly.