perf: Optimize login latency and reduce redundant I/O in solidui/pod/auth

[Miduo666]

Description

A performance audit of the login flow has identified several bottlenecks across solidui, solidpod, and solid_auth. The current implementation suffers from redundant network calls, expensive serial I/O, and unnecessary UI blocking.

Identified Issues

1. Redundant Network Requests (P1)
   Duplicate Profile Fetches: getIssuer() and solidAuthenticate() both fetch the WebID profile independently; the second call should reuse the first.

Redundant Session Refresh: solidAuthenticate() triggers a GET request for the profile card even when a valid session is cached.

No Issuer Caching: getIssuer() re-parses the RDF and fetches the profile on every call.

2. Excessive Local I/O & Deserialization (P2)
   Repeated State Checks: isUserLoggedIn() is called multiple times, triggering redundant secure storage reads.

JSON/JWT Overhead: TokenResponse.fromJson() and JwtDecoder are executed for every resource access (e.g., 13 parallel requests trigger 13 identical decodes).

3. Serial I/O Bottlenecks (P3)
   Synchronous initialization: initPod() handles directory resolution, key file parsing, and file creation (PUT/POST) using serial await loops. These should be executed in parallel where no data dependency exists.

4. UI Blocking (P4)
   Eager Initialization: SolidLogin blocks the initial frame until all folder/file generation and package info parsing are complete.

Inefficient Rebuilds: _initPackageInfo() triggers multiple setState() calls, causing unnecessary UI reconstructions.