restructure: update user data handling to allow server-side authentication

[Xyphyn]

big branch:

Photon currently is a client-side only app, with optional guest SSR. This works great as a web app, but not for SEO. While you can enable SSR for SEO, it is not authenticated and will lead to a flash of content from a guest user instead of your profile--making things clunky for actual users.

this pr aims to do the following:

• Rewrite app-side data to use a unified userHost object that can be filled with either data from a cookie, or localStorage.
  • this will allow for a hybrid mode, where you can either use server-side user data or client-side user data.
• userHost data is stored in a JSON state, but can be loaded into reactive classes for the client/rendering.
• Instead of using global state in the form of profile or settings objects, use Svelte's getContext and setContext to access this data.
• Maintain a near-identical user experience for client-side instances, such as at phtn.app.

[cloudflare-workers-and-pages]

Deploying photon with    Cloudflare Pages

Latest commit:	1dbe27b
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