Add Slice 4 tuner stack with AGENTS-compliant core types and HTTP API.

Introduces Si4684/ADAU1701 drivers, TunerService, FrequencyKHz,
SeekDirection, /api/tuner routes without file-scope globals, host tests,
and firmware blob tooling (binaries remain gitignored).

Co-authored-by: Cursor <cursoragent@cursor.com>

Software/components/services/tuner/CMakeLists.txt

@@ -0,0 +1,8 @@
+idf_component_register(
+    SRCS
+        "src/TunerService.cpp"
+    INCLUDE_DIRS "include"
+    REQUIRES core
+)
+
+target_compile_features(${COMPONENT_LIB} PUBLIC cxx_std_23)