feat: fluid viewport canvas scaling and responsive hero margins

[google-labs-jules]

Summary

This PR implements fluid viewport scaling for horizontal canvas drawing offsets and responsive hero overlay top spacing on the landing page.

Key Changes

• Fluid Viewport Offset Scaling: Dynamic calculation of scaleFactor = Math.min(1, w / 1024) in +page.svelte canvas setup and resizeObserver. Horizontal offsets for both the bar chart and network graph elements scale dynamically based on active viewport width, ensuring canvas drawings render without passing through centered header text on viewports down to 320px width while preserving baseline desktop visual positioning at widths of 1024px and above.
• Responsive Tailwind Margins: Replaced fixed inline offset (style="margin-top: 12rem;") on the hero text container with responsive utility classes (mt-16 sm:mt-24 md:mt-36 lg:mt-48). Top margins contract automatically on shorter screen heights (down to 560px), keeping primary navigation links unobstructed and easily targetable.
• Resize Observer Recalculation: Scale factors and center positions automatically recalculate during window resize events for smooth transitions.
• Unit Testing: Added src/routes/page.spec.ts verifying scale factor calculations across breakpoints and checking that responsive Tailwind margin utility classes are present without inline style overrides.

Verification

• bun run check: 0 errors, 0 warnings.
• bun run test: 16 passed, 61 passed tests.
• bun run build: Built successfully.