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/layer.sexp

@@ -0,0 +1,36 @@
+;; Layer effect - composite overlay over background at position
+;; Streaming-compatible: frame is background, overlay is foreground
+;; Usage: (layer background overlay :x 10 :y 20 :opacity 0.8)
+;;
+;; Params:
+;;   overlay - frame to composite on top
+;;   x, y - position to place overlay
+;;   opacity - blend amount (0-1)
+;;   mode - blend mode (alpha, multiply, screen, etc.)
+
+(require-primitives "image" "blending" "core")
+
+(define-effect layer
+  :params (
+    (overlay :type frame :default nil)
+    (x :type int :default 0)
+    (y :type int :default 0)
+    (opacity :type float :default 1.0)
+    (mode :type string :default "alpha")
+  )
+  (if (core:is-nil overlay)
+    frame
+    (let [bg (copy frame)
+          fg overlay
+          fg-w (image:width fg)
+          fg-h (image:height fg)]
+      (if (= opacity 1.0)
+        ;; Simple paste
+        (paste bg fg x y)
+        ;; Blend with opacity
+        (let [blended (if (= mode "alpha")
+                        (blending:blend-images (image:crop bg x y fg-w fg-h) fg opacity)
+                        (blending:blend-images (image:crop bg x y fg-w fg-h)
+                                     (blending:blend-mode (image:crop bg x y fg-w fg-h) fg mode)
+                                     opacity))]
+          (paste bg blended x y))))))