[guiyanakuang]

Removes the newest/oldest sort toggle from the search window, together with the sort state behind it (SearchBaseParams.sort, SearchParams.sort, PasteSearchViewModel.switchSort()). Search results are always newest first.

Why:

• The search window is keyboard driven: open it and press Enter to paste the first result, which is the latest copy. With the toggle flipped, Enter pastes the oldest record instead, and the order stays flipped for the rest of the session, so one accidental click keeps pasting the wrong item.
• Oldest-first is rarely what clipboard history is used for; search, type and tag filters already cover finding older items.
• The mobile apps drop the same toggle (pasteboard and keyboard), and they share this view model through the synced common code.

The DAO-level sort parameter stays: the CLI history?sort= option, MCP tools and the mobile widgets/shortcuts still use it.

Also removes the now-unused sort_newest_first / sort_oldest_first strings.

Verification: ./gradlew :app:desktopTest for PasteSearchViewModel, GeneralPasteSearchViewModel, PastePanelViewModel and the i18n consistency/copywriter tests (51 tests, all pass).

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