feat: disable auto-resolve and memory caching when cache is off

[wind-hx]

These changes unify “reduce extra requests when cache is disabled” under a single flag and prevent in‑memory caching when cache is off. A new DisableAutoResolve is introduced (auto‑enabled when DisableCache is true), so message processing no longer fetches min users/channels from the server, and all cache fetch paths become cache‑only in that mode. Cache updates are also skipped when disabled, ensuring no file writes and no in‑memory retention.

Files touched:

client.go: add/enable DisableAutoResolve with DisableCache
helpers.go: skip min user/channel auto resolve; getSender is cache‑only
cache.go: skip memory updates when disabled; cache fetches are cache‑only under DisableAutoResolve

[AmarnathCJD]

@wind-hx No

[wind-hx]

@AmarnathCJD I hope to reduce unnecessary requests through configuration.

[AmarnathCJD]

@wind-hx That would break event handlers

[wind-hx]

Not all events need to be processed. When user messages or channel messages are received, the processing authority can be given to the developers themselves, who can decide whether or not to obtain the sender information.