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

Re-introduce after the iter5b-α' revert. Helper maps VAProfile to V4L2
OUTPUT-side FOURCC, used at CreateConfig in commit B to populate the
previously-dead object_config->pixelformat field. β reads from there
at CreateContext (commit C).

Single source of truth for the profile→pixelformat mapping; mirrors
the per-profile probes in config.c::RequestQueryConfigProfiles
(lines 138-188).

Register codec.c in meson.build sources, codec.h in 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 = [