feat: add tRPC auth context, middleware, and protected procedures
- Install jose (JWT) and bcryptjs (password hashing) dependencies
- Create auth utilities: JWT sign/verify, password hash/verify, session management
- Create createTRPCContext that extracts auth from session cookie, Bearer JWT, or x-api-key
- Add publicProcedure, protectedProcedure, adminProcedure, rateLimitedProcedure with middleware
- Wire context builder into SolidStart tRPC API handler
- Update tRPC client to inject auth tokens and handle 401 redirects
- Add unit tests for JWT, password, context builder, and middleware