feat(history): batch delete for recognition history + test alignment

[MangoWAY]

Summary

This PR adds batch delete for Settings → History (recognition history), refactors selection logic into a small testable helper, extends HistoryStore with a transactional multi-row delete, and aligns several XCTest suites with the current production behavior (AssemblyAI, Soniox, Volcano, AppState, ModeStorage).

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Features (user-visible)

Batch delete in History tab

• Select button enters selection mode; Done exits and clears selection.
• In selection mode, each row shows a checkbox; clicking the row or the checkbox toggles selection.
• Toolbar: N selected, Select all in list / Deselect all when the current filtered list is fully selected, and Delete (disabled when nothing is selected).
• Select all applies only to the currently loaded + filtered rows (same semantics as infinite scroll elsewhere).
• Delete shows a confirmation alert (destructive).
• Search clears the current selection; leaving the History tab clears selection mode.
• Per-row actions (Correct / Copy / single Delete) are hidden in selection mode to reduce mis-taps.
• Export is disabled while in selection mode.

Data layer

• HistoryStore.delete(ids: [String]): runs in a single SQLite transaction, deletes in chunks of up to 500 IDs (SQLite variable limit), posts historyStoreDidChange once on success.

Testability

• HistorySelectionHelpers: pure functions for “all filtered selected?” and toggle select-all / deselect-all; covered by HistorySelectionHelpersTests.
• HistoryStoreTests: batch delete, empty-ID no-op, notification expectation; HistoryRecord initializers updated with asrProvider: nil where needed.

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Test suite fixes (why they changed)

These are not behavioral changes to those subsystems in this PR; tests were outdated vs current code:

Area	Change
AppState	finalize only runs when barPhase == .processing; test sets phase before calling.
AssemblyAI	Keyterms moved off the WebSocket URL to UpdateConfiguration after connect; URL tests assert absence of keyterms_prompt and validate updateConfigurationMessage.
Soniox	Start payload context is only { "terms": [...] } (no general block).
Volcano	When boostingTableID is set, inline hotwords context is omitted (table wins); split expectations + new test for hotwords-only.
ModeStorage	Legacy formal-writing migration resets processingLabel to the current default; assertion compares to ProcessingMode.formalWriting.processingLabel.

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Risks & limitations

1. Batch delete scope: Deletes only selected rows that are already loaded in the UI. Users who need to delete “everything in DB” without scrolling must still rely on multiple loads or a future “clear all” (out of scope here).
2. Search + selection: Changing the search text clears selection (intentional, avoids deleting stale IDs).
3. Double notification: After batch delete, historyStoreDidChange triggers a full reload of the first page; acceptable and consistent with single-row delete.
4. Test alignment: Owners should be aware that test updates encode current AssemblyAI/Soniox/Volc/AppState contracts; if upstream intentionally diverges, those tests may need revisiting.

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How to verify

swift build -c release
swift test

Manually: Settings → History → Select → select rows → Delete → confirm.

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Checklist

• Builds (swift build -c release)
• Tests pass (swift test)
• New strings use existing L(zh, en) pattern where applicable