fix: load .env before config cache to prevent null env values on startup

[techmahedy]

Root cause

On application startup, Config::initialize() was called inside withConfiguration() before EnvServiceProvider had loaded the .env file. This meant every env() call inside config/*.php returned null. The resulting null-value config was then written to the cache file, and all subsequent requests served those stale null values — even after the process restarted and the .env was available.

A secondary issue:

The cache key was computed from the hashes of config/*.php files only. Changing .env did not invalidate the cache because the .env hash was not included in the key. The static memoisation on isCacheValid() also locked the result to false for the entire request lifetime, preventing recovery after the first miss.