Polish MD3E: icon, splash, colors, layout

[danielchalmers]

Round of Material 3 Expressive polish following recent PRs:

• The launcher glyph was filling ~94% of the adaptive icon's visible circle. The foreground SVG is scaled to 75% so the smiley sits at the Material 52dp circular keyline, and the monochrome layer's inset drops from 18% to 7% so the themed icon stays the size it already was.
• Android 12+ no longer sets a custom splash icon, so the system shows the real launcher icon with its pink plate and platform mask instead of the non-standard bare glyph. Pre-12 approximates the same look with a drawn plate behind the glyph.
• The splash background switches from full-screen pink to the theme background tones (light #FFF8F9 / dark #181215), and the Blazor loading screen uses the same hexes instead of the browser's Canvas color, so splash, loading screen, and app read as one continuous surface.
• The dark-mode white flash between splash and loading screen is gone: the page has a themed background and BlazorWebViewInitialized makes the native WebView transparent (Android and Windows) so that background shows through until Blazor's first paint.
• The straight-face mood color in the calendar is now a neutral grey (#D9D9D9 light / #737373 dark) instead of sand/brown, keeping the same lightness as its ramp neighbors.
• Segmented controls drop their checkmarks, matching M3E connected button groups where selection reads from the filled container. This also stops long labels like "Moderate" from overflowing at large font scales and removes the width jump on selection.
• The sleep readout gets a fixed width with tabular numerals so 9.5 -> 10.0 no longer shifts the slider.
• A soft level-1 shadow fades in under the sticky header via scroll-driven animation once content passes beneath it. MD3 proper would retone the container, but that desyncs the natively colored status bar while the app is letterboxed, so elevation stands in until edge-to-edge (Theme the system navigation bar for edge-to-edge #110) lands. Browsers without scroll-timeline support keep the current flat look.
• README mentions Material You, the M3E theming on MudBlazor, and haptics.