Initial commit: video effects processing system

Add S-expression based video effects pipeline with modular effect
definitions, constructs, and recipe files.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

sexp_effects/effects/hue_shift.sexp

@@ -0,0 +1,9 @@
+;; Hue shift effect - rotates hue values
+;; @param degrees float [0, 360] default 0
+;; @param speed float default 0 - rotation per second
+;; Uses vectorized shift-hsv primitive for fast processing
+
+(define-effect hue_shift
+  ((degrees 0) (speed 0))
+  (let ((shift (+ degrees (* speed t))))
+    (shift-hsv frame shift 1 1)))