Replace batch DAG system with streaming architecture

- Remove legacy_tasks.py, hybrid_state.py, render.py
- Remove old task modules (analyze, execute, execute_sexp, orchestrate)
- Add streaming interpreter from test repo
- Add sexp_effects with primitives and video effects
- Add streaming Celery task with CID-based asset resolution
- Support both CID and friendly name references for assets
- Add .dockerignore to prevent local clones from conflicting

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

sexp_effects/effects/pixelate.sexp

@@ -0,0 +1,13 @@
+;; Pixelate effect - creates blocky pixels
+(require-primitives "image")
+
+(define-effect pixelate
+  :params (
+    (block_size :type int :default 8 :range [2 64])
+  )
+  (let* ((w (image:width frame))
+         (h (image:height frame))
+         (small-w (max 1 (floor (/ w block_size))))
+         (small-h (max 1 (floor (/ h block_size))))
+         (small (image:resize frame small-w small-h "area")))
+    (image:resize small w h "nearest")))