Add Wan2.2-I2V-A14B image-to-video support to the video backend

Wan-AI/Wan2.2-I2V-A14B-Diffusers is the image-to-video sibling of the already
supported T2V-A14B: the same dual-expert WanTransformer3DModel pair (boundary_ratio
0.9 in the pipeline config) behind WanImageToVideoPipeline, conditioning through the
VAE latent (no CLIP-vision image encoder in this 2.2 variant).

- New wan2.2-i2v-a14b family: image_conditioned flag, card recipe defaults (40 steps,
  CFG 3.5, 81 frames at 16 fps), the T2V memory table (57.2 GB both experts bf16),
  fp32-pinned VAE, and a wan2.2-i2v generation-defaults key ahead of the generic wan
  50/5.0 entry.
- Source-image plumbing: /video/generate takes init_image (base64/data URL);
  begin_generate 400s synchronously when an image-to-video family has no image or a
  text-only family is given one, and generate() decodes and resizes the image to the
  snapped output size before threading it as the pipeline's image kwarg. status()
  reports image_input so the UI can gate the control.
- Trust the official -Diffusers repo for pipeline loads and transfer the measured wan
  quant recipes: fp8 keeps condition_embedder in bf16 (zero padding-row scale), mxfp8
  and nvfp4 stay denied, the UMT5 auto TE quant resolves dense, and the balanced
  FBCache pin carries over. All tables share the T2V DiT profile.
- Tests: family detection/aliases/defaults, the dual-DiT image pipeline load, the
  image gates on both begin_generate and generate, init_image route pass-through, and
  the quant exclude/deny/auto entries.

GPU-verified on a B200: bf16 resident load (offload none, 72.8 GB peak) animating a
conditioning image at 832x480/33f in 28.7 s with first-frame MAE 5.7 vs the source,
and an int8 load with both experts quantized (43.1 GB peak, clean output).

studio/backend/core/inference/diffusion_cache.py

@@ -89,6 +89,8 @@ _FBCACHE_QUALITY_THRESHOLDS: dict[str, tuple[float, float]] = {
 # 0.08 is the least-drift cache-on point, not a compliant one.
 _FAMILY_FBCACHE_THRESHOLDS: dict[tuple[str, str], tuple[float, float]] = {
     ("wan2.2-t2v-a14b", CQ_BALANCED): (DEFAULT_FBCACHE_THRESHOLD, DEFAULT_FBCACHE_THRESHOLD),
+    # I2V-A14B shares the T2V DiT pair; inherit the balanced pin (same drift profile).
+    ("wan2.2-i2v-a14b", CQ_BALANCED): (DEFAULT_FBCACHE_THRESHOLD, DEFAULT_FBCACHE_THRESHOLD),
 }