CMakeLists: install rules + pkg-config for daedalus_core

Make daedalus_core installable so sibling consumers (Phase 8 V4L2
daemon, future libva-v4l2-request-fourier integration tests, etc.)
can `pkg_check_modules(DAEDALUS REQUIRED daedalus-fourier)` against
a system-installed copy.

Installs:
  - lib/libdaedalus_core.a
  - include/daedalus.h
  - lib/pkgconfig/daedalus-fourier.pc
  - share/daedalus-fourier/shaders/*.spv  (only when
    DAEDALUS_BUILD_VULKAN is ON; consumers using
    daedalus_ctx_create_no_qpu() don't need them)

pkg-config surfaces the static-archive transitive deps via
Libs.private (-lpthread -ldl -lm) and Requires.private (vulkan),
so a consumer doing `pkg-config --static --libs daedalus-fourier`
gets the full link line.  Non-static consumers (using the
no_qpu path) get just `-ldaedalus_core`.

No behaviour change to existing tests / benches.

Verified on hertz (Pi 5, dev host): clean build, all 7 SPIR-V
shaders + the static lib + the header + the .pc file land in
the install prefix.

CMakeLists.txt

@@ -376,6 +376,68 @@ if (DAEDALUS_BUILD_VULKAN)
     add_dependencies(daedalus_core daedalus_shaders)
 endif()
 
+# ---- Install rules for sibling consumers (Phase 8 V4L2 daemon, etc.) -------
+#
+# Installs:
+#   - libdaedalus_core.a   → ${CMAKE_INSTALL_LIBDIR}
+#   - include/daedalus.h   → ${CMAKE_INSTALL_INCLUDEDIR}
+#   - daedalus-fourier.pc  → ${CMAKE_INSTALL_LIBDIR}/pkgconfig
+#   - V3D SPIR-V shaders   → ${CMAKE_INSTALL_DATADIR}/daedalus-fourier/shaders
+#     (only when DAEDALUS_BUILD_VULKAN is ON; consumers using
+#     daedalus_ctx_create_no_qpu() don't need them)
+#
+# pkg-config tells consumers what to link; the static-archive
+# dependencies (Vulkan, pthread, and the vendored asm symbols)
+# are surfaced through Requires.private + Libs.private so a
+# consumer doing `pkg-config --libs daedalus-fourier` gets the
+# right transitive link line.
+
+include(GNUInstallDirs)
+
+install(TARGETS daedalus_core
+    ARCHIVE DESTINATION ${CMAKE_INSTALL_LIBDIR}
+)
+
+install(FILES include/daedalus.h
+    DESTINATION ${CMAKE_INSTALL_INCLUDEDIR}
+)
+
+if (DAEDALUS_BUILD_VULKAN)
+    install(FILES
+        ${NOOP_SPV}
+        ${IDCT8_SPV}
+        ${LPF_SPV}
+        ${MC_SPV}
+        ${LPF8_SPV}
+        ${CDEF_SPV}
+        ${H264DEBLOCK_SPV}
+        DESTINATION ${CMAKE_INSTALL_DATADIR}/daedalus-fourier/shaders
+    )
+endif()
+
+# pkg-config file.  Vulkan goes in Requires.private (consumer's
+# pkg-config call gets it via --static).  pthread + dl are needed
+# by the static archive's runtime helpers.
+set(PKGCONFIG_OUT ${CMAKE_CURRENT_BINARY_DIR}/daedalus-fourier.pc)
+file(WRITE ${PKGCONFIG_OUT}
+"prefix=${CMAKE_INSTALL_PREFIX}
+exec_prefix=\${prefix}
+libdir=\${prefix}/${CMAKE_INSTALL_LIBDIR}
+includedir=\${prefix}/${CMAKE_INSTALL_INCLUDEDIR}
+shadersdir=\${prefix}/${CMAKE_INSTALL_DATADIR}/daedalus-fourier/shaders
+
+Name: daedalus-fourier
+Description: VP9/AV1/H.264 back-end kernels for VC VII (V3D 7.1) + ARM NEON
+Version: 0.1.0
+Libs: -L\${libdir} -ldaedalus_core
+Libs.private: -lpthread -ldl -lm
+Requires.private: vulkan
+Cflags: -I\${includedir}
+")
+install(FILES ${PKGCONFIG_OUT}
+    DESTINATION ${CMAKE_INSTALL_LIBDIR}/pkgconfig
+)
+
 add_executable(test_api_idct
     tests/test_api_idct.c
     tests/vp9_idct8_ref.c