fresnel-fourier iter5b Phase 6 commit A: NEW src/codec.{h,c} — pixelformat_for_profile helper

Add a small helper that maps a VAProfile to its V4L2 OUTPUT-side
pixel format FOURCC. Single source of truth, mirrors the per-profile
probes in config.c::RequestQueryConfigProfiles (lines 138-188).

Used by commits B + C in this series:
- commit B: populate object_config->pixelformat at CreateConfig
- commit C: surface.c reads the populated field to set OUTPUT format
  per-profile instead of hardcoded H264_SLICE

Register in meson.build sources + headers.

Signed-off-by: claude-noether <claude-noether@reauktion.de>

src/meson.build

@@ -49,7 +49,8 @@ sources = [
 	'cap_pool.c',
 	'h265.c',
 	'vp8.c',
-	'vp9.c'
+	'vp9.c',
+	'codec.c'
 ]
 
 headers = [
@@ -74,7 +75,8 @@ headers = [
 	'cap_pool.h',
 	'h265.h',
 	'vp8.h',
-	'vp9.h'
+	'vp9.h',
+	'codec.h'
 ]
 
 includes = [