User accounts

Allows for the creation of user accounts. A few notes on the specifics:

 - Experiments are the main access control objects. If you can view an experiment, you can view all its prompts/scenarios/evals. If you can edit it, you can edit or delete all of those as well.
 - Experiments are owned by Organizations in the database. Organizations can have multiple members and members can have roles of ADMIN, MEMBER or VIEWER.
 - Organizations can either be "personal" or general. Each user has a "personal" organization created as soon as they try to create an experiment. There's currently no UI support for creating general orgs or adding users to them; they're just in the database to future-proof all the ACL logic.
 - You can require that a user is signed-in to see a route using the `protectedProcedure` helper. When you use `protectedProcedure`, you also have to call `ctx.markAccessControlRun()` (or delegate to a function that does it for you; see accessControl.ts). This is to remind us to actually check for access control when we define a new endpoint.

@types/nextjs-routes.d.ts

@@ -11,6 +11,7 @@ declare module "nextjs-routes" {
   } from "next";
 
   export type Route =
+    | StaticRoute<"/account/signin">
     | DynamicRoute<"/api/auth/[...nextauth]", { "nextauth": string[] }>
     | DynamicRoute<"/api/trpc/[trpc]", { "trpc": string }>
     | DynamicRoute<"/experiments/[id]", { "id": string }>