Fix squashed rendering on iOS (safe-area surface size mismatch)

[nicoburns]

Summary

On iOS the rendered content appeared vertically squashed. The root cause was a size mismatch between the document viewport and the render surface: SurfaceResized already sets the document viewport to surface_size - safe_area_insets (and with_viewport sizes the renderer at viewport + insets), but the initial View::init viewport and resume/complete_resume used inconsistent sizes. The wgpu surface ended up configured at the inset-adjusted height while covering the full window, so Vello's output was stretched/squashed to fit.

Fix (all in blitz-shell/src/window.rs):

• init: create the initial Viewport at surface_size - safe_area_insets instead of the full surface size, matching what SurfaceResized later computes.
• resume/complete_resume: size the render surface at viewport + insets (the full window), matching with_viewport.
• complete_resume/redraw: pass physical insets to paint_scene instead of insets.to_logical(scale) — initial_x/initial_y are consumed as physical pixels (see the unit note in debug_overlay.rs), so logical values placed content under the notch on 3x displays.

Also in blitz-paint/src/render.rs: the background rect used initial_x * scale, double-scaling the already-physical offset; now uses initial_x/initial_y directly, consistent with the element transform path.

No behavior change on platforms with zero safe-area insets (including macOS, where insets are hardcoded to zero).

Verified on an iPhone 17 simulator (3x scale, insets top=186/bottom=102 physical):

Before	After

Link to Devin session: https://dioxus.staging.devinenterprise.com/sessions/4cdd57b070834fc8af874a8aed768c65
Requested by: @nicoburns

WPT results

No changes in test results compared to main.

_{Generated by the WPT workflow.}

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