fix: improve LCP by SSR-ing welcome screen and preloading hero images

[hhvrc]

• SSR the welcome screen for new visitors using a cookie read in +layout.server.ts
• Unmount it via a close callback once dismissed
• Add <link rel="preload"> and fetchpriority="high" to hero SVGs on the home page and welcome screen
• Migrate welcome state from localStorage to cookies so the server can skip rendering it on return visits
• Fix hasSeenWelcome() to check cookies so the deferred tour prompt still works for new users

[Copilot]

Pull request overview

This PR aims to improve LCP for first-time visitors by server-rendering the welcome screen based on a cookie, and by preloading/prioritizing hero SVGs so critical imagery is available earlier in the render path.

Changes:

• SSR-gate the welcome screen via +layout.server.ts and unmount it via a close callback from +layout.svelte.
• Migrate “welcome seen” state from localStorage to a cookie (with a localStorage fallback for migration) and update checks accordingly.
• Add <link rel="preload"> and fetchpriority="high" to key SVG assets on the home page and welcome screen.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
src/routes/WelcomeScreen.svelte	Converts welcome rendering to be parent-controlled (SSR-visible), adds preload + fetchpriority, and introduces a close() prop for unmounting.
src/routes/+page.svelte	Preloads and prioritizes the home page hero SVGs for faster first paint/LCP.
src/routes/+layout.svelte	Conditionally mounts/unmounts WelcomeScreen based on SSR-provided data.showWelcome.
src/routes/+layout.server.ts	Reads the welcome cookie to decide whether the welcome screen should be SSR-rendered.
src/lib/tour/onboarding-state.ts	Switches welcome state to cookies (with migration fallback) and updates hasSeenWelcome()/markWelcomed().

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[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 3 comments.