feat(gallery): add Depth Anything V2 models + bump native version

Add Depth Anything V2 (DA2) support to the depth-anything backend. DA2 is
depth-only (no camera pose, no confidence) and ships both relative
(relative inverse depth) and metric (depth in metres) variants. The Go
backend is model-agnostic, so no backend code changes are required — only
a native version bump and new gallery entries.

- backend/go/depth-anything-cpp/Makefile: pin DEPTHANYTHING_VERSION to the
  depth-anything.cpp commit that adds the DA2 engine + C-API routing
  (e3dec57f13a52366bbc4f279ef44804915960a6b, kept alive by the upstream tag
  da2-support so it survives a squash-merge).
- gallery/index.yaml: add 12 DA2 entries (4 base quants, small, large, plus
  Hypersim indoor and VKITTI outdoor metric models in S/B/L). Metric models
  carry the metric-depth tag; none carry camera-pose.

Assisted-by: Claude:claude-opus-4-8

backend/go/depth-anything-cpp/Makefile

@@ -8,11 +8,13 @@ JOBS?=$(shell nproc --ignore=1)
 
 # depth-anything.cpp. Pin to a specific commit for a stable build; a squash
 # merge upstream can orphan a branch, so the native version is pinned by SHA.
-# This SHA adds the nested two-file metric C-API (abi_version 4,
-# da_capi_load_nested) required by the depth-anything-3-nested gallery model;
-# tag it (e.g. v0.1.3) upstream to keep the SHA alive.
+# This SHA adds the Depth Anything V2 engine + C-API routing (depth-only,
+# relative + metric) on top of the nested two-file metric C-API (abi_version 4,
+# da_capi_load_nested) required by the depth-anything-3-nested gallery model.
+# It is kept alive by the upstream tag da2-support (survives a squash-merge);
+# repoint to the master merge commit once mudler/depth-anything.cpp PR #1 lands.
 DEPTHANYTHING_REPO?=https://github.com/mudler/depth-anything.cpp.git
-DEPTHANYTHING_VERSION?=cce5edc395fd1843806093d7ccc0c8b0d0b97b72
+DEPTHANYTHING_VERSION?=e3dec57f13a52366bbc4f279ef44804915960a6b
 
 ifeq ($(NATIVE),false)
 	CMAKE_ARGS+=-DGGML_NATIVE=OFF