feat(logs): add log download via File/Current and Range endpoints

[harshithmohan]

Summary

Adds a Download logs action to the Logs page. It downloads the current log file when no filters are active, and downloads the full filtered log history (matching the active search/level filters) when they are.

Changes

Added

• logging/mutations.ts — useLogsDownloadMutation: hits Logging/File/Current/Download when no filters are active, Logging/Range/Download with level/message params otherwise; saves the response blob via an object-URL anchor click with a shoko-logs-<timestamp>.txt filename.
• logging/helpers.ts — toServerSearch (with private hasDslPrefix) moved here from LogSearchView.tsx so the search and download paths share one DSL wrapping.
• LogsPage.tsx — download icon button next to clear filters; spinner/disabled state while in flight; error toast on failure.
• IconButton.tsx — additive loading prop forwarded to Button.

Fixed

• LogSearchView.tsx — imports toServerSearch from the shared helpers module (local copies removed).