[Chore]: Configure bounded Kingfisher cache limits

[dong4j]

Problem

Image caching does not have an explicitly accepted memory and disk budget.

Expected Behavior

Kingfisher cache limits and expiration behavior are configured for Starcat's workload.

Scope

• Deliver the outcome described above in the owning repository.
• Preserve existing behavior outside this focused scope.
• Record implementation and acceptance evidence in this Issue.

Acceptance Criteria

• Memory and disk limits are explicit and documented near configuration.
• Cache eviction does not break repository image fallbacks.
• Validate behavior under a representative large repository list.

Context

Migrated from docs/功能实现总览.md:1715 during the organization-wide Starcat backlog migration on 2026-08-21. This Issue records pending work only; it does not claim that implementation or validation has completed.