Add a results archive and purge orphaned passing rows on delete

Until now there was no way to find a completed session without already
knowing which event it belonged to - navigation was strictly Events ->
one event -> its sessions. A new "Resultatarkiv" view lists every
finished session across all events, searchable by event/session name,
class, driver and date range.

Opening a session reuses the existing single-session leaderboard
builder for standings and the existing per-competitor lap lookup for
lap history - no new results logic - plus a session-wide penalties/
corrections list (resultsBySession[id].adjustments), previously only
visible in the live judging action log. Export buttons reuse the
existing per-event PDF and race-package JSON export functions rather
than adding a new format.

Investigated what should happen to raw timing data when a race is
deleted. Training statistics and session replay already read from
their own independent, deliberately-retained copies that survive
deletion by existing design - unaffected either way. The one thing
that outlived deletion with no purpose was the raw `passings` SQLite
rows (write-only; nothing in the app reads them), growing forever with
driver IDs never purged. A new POST /api/passings/purge endpoint now
removes exactly the deleted session(s)' rows, called as a best-effort
side call from both delete-event and delete-session.

Also fixes a real bug found while building this: ensureSessionResult
guarded adjustments/splits/pitEvents/pitStops against being missing on
an already-existing result, but not passings itself, so viewing lap
history for such a result (e.g. an older/imported race package)
crashed outright.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

CHANGELOG.md

@@ -8,6 +8,16 @@ The application version is maintained in `package.json` and displayed in the adm
 
 No changes recorded yet.
 
+## 1.6.0 - 2026-09-09
+
+### Added
+
+- A new "Resultatarkiv" (results archive) view lists every completed session across all events, searchable by event/session name, class, driver and date - no more needing to already know which event a session belonged to. Opening a session shows its standings, penalties/corrections, and a per-driver lap history, and offers the same PDF and race-package (JSON) export already available from Event Manager. Deleting an event or session now also removes its raw timing rows from the database instead of leaving them behind indefinitely - driver-visible training statistics and session replay are unaffected, since they already keep their own independent copy.
+
+### Fixed
+
+- Opening a session's lap history in the archive (or anywhere reusing the same lookup) crashed if that session's result was missing its passings list - e.g. an older or hand-edited/imported race package. It's now backfilled the same way other missing result fields already were.
+
 ## 1.5.0 - 2026-09-09
 
 ### Added