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>

src/event_workspace_controller.js

@@ -37,6 +37,7 @@ export function renderEventWorkspaceView(context) {
     bindModalShell,
     isValidIsoDate,
     saveState,
+    purgeSessionPassings,
     openTimingSession,
   } = context;
 
@@ -281,6 +282,7 @@ export function renderEventWorkspaceView(context) {
         state.activeSessionId = null;
       }
       saveState();
+      void purgeSessionPassings(sessionIds);
       renderView();
     });