M11.4: Lottie export/import

New crate effectcraft-lottie (L3): export a comp to Lottie JSON / dotLottie
(precomp and base64 image assets; shape, solid, null, precomp, image and text
layers or glyph shapes; transforms with parenting, separated position,
anchor; keyframes with speed/influence converted to normalised i/o tangents,
hold keys, spatial ti/to; all shape items incl. gradients, dashes, trim,
repeater and path operators; masks, track mattes, blend modes, time remap,
timing, markers, optional expressions, a few Lottie effects) with a warnings
list for what Lottie cannot express, and the inverse import. Commands
file.exportLottie / file.importLottie with File > Export / Import entries.
Round-trip tests (values and rendered frames) and hand-written fixtures.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Cargo.lock

@@ -1191,6 +1191,7 @@ dependencies = [
  "effectcraft-effects",
  "effectcraft-geom",
  "effectcraft-keyframe",
+ "effectcraft-lottie",
  "effectcraft-path",
  "effectcraft-project",
  "effectcraft-raster",
@@ -1275,6 +1276,23 @@ dependencies = [
  "serde_json",
 ]
 
+[[package]]
+name = "effectcraft-lottie"
+version = "0.1.0"
+dependencies = [
+ "effectcraft-color",
+ "effectcraft-effects",
+ "effectcraft-keyframe",
+ "effectcraft-path",
+ "effectcraft-project",
+ "effectcraft-render",
+ "effectcraft-text",
+ "effectcraft-time",
+ "kurbo",
+ "serde_json",
+ "thiserror 2.0.21",
+]
+
 [[package]]
 name = "effectcraft-media"
 version = "0.1.0"