fix(backend): call vram.EstimateModelMultiContext for model size estimate
core/backend/options.go called vram.EstimateModel, which does not exist in
the vram package (it exposes EstimateModelMultiContext). This broke the build
on master (undefined: vram.EstimateModel). Use EstimateModelMultiContext with
a nil context-size slice (defaults to a single 8192 estimate); the returned
MultiContextEstimate.SizeBytes is exactly what the caller consumes, so size
estimation behavior is unchanged.
Assisted-by: Claude:claude-opus-4-8
Signed-off-by: Ettore Di Giacinto <mudler@localai.io>
Co-authored-by: Ettore Di Giacinto <mudler@localai.io>
7b462a0d51