feat(phase-8-backend): per-event results harvesting + EventPath plumbing

Implements Phase 8 Amendment 1: marathonbet.by has no public results archive
endpoint, so results must be harvested per-event by re-fetching the event
detail page until eventJsonInfo.matchIsComplete=true.

Backend changes:

* IOddsScraper:
  - ScrapeResultsAsync(DateRange) replaced with ScrapeEventResultAsync(Event)
    returning a nullable EventResult — null when match still in progress.
  - ScrapeEventOddsAsync now takes the full Event (so EventPath drives URL
    construction) instead of bare EventId.
  - New ScrapeLiveAsync() for the /su/live listing.

* Domain:
  - Event gains EventPath (nullable string) — the data-event-path attribute
    captured during scraping; required for reliable URL construction.

* Infrastructure:
  - New migration 20260506000000_AddEventPath adds the column.
  - EventEntity / EventConfiguration / Mapping / model-snapshot updated.
  - MarathonbetScraper: new ScrapeLiveAsync + ScrapeEventResultAsync; URL
    builder prefers EventPath, falls back to numeric ID for legacy rows.
  - EventListingParserBase extracts data-event-path on every listing row.

* Application:
  - PullResultsUseCase: branches on selection vs date-range, emits IProgress<
    PullResultsProgress>, returns ResultLoadOutcome (Loaded / AlreadyLoaded /
    NotYetComplete / Failed); idempotent (skips events whose result already
    exists).
  - PullLiveOddsUseCase now drives off the live listing (auto-discovers
    events that go live without ever appearing in the upcoming list) and
    backfills EventPath on legacy rows.
  - PullUpcomingEventsUseCase wires EventPath on persisted events.

* Workers: UpcomingEventsPoller updates persistence path accordingly.

* Tests: 17 net-new tests across Application + Infrastructure + Domain;
  all 293 still pass.

src/Marathon.Infrastructure/Persistence/Mapping.cs

@@ -24,6 +24,7 @@ internal static class Mapping
             ScheduledAt = domain.ScheduledAt.ToString("O"),
             Side1Name = domain.Side1Name,
             Side2Name = domain.Side2Name,
+            EventPath = domain.EventPath,
         };
 
     public static Event ToDomain(EventEntity entity) =>
@@ -35,7 +36,10 @@ internal static class Mapping
             Category: entity.Category,
             ScheduledAt: DateTimeOffset.Parse(entity.ScheduledAt),
             Side1Name: entity.Side1Name,
-            Side2Name: entity.Side2Name);
+            Side2Name: entity.Side2Name)
+        {
+            EventPath = entity.EventPath,
+        };
 
     // ─── OddsSnapshot ─────────────────────────────────────────────────────────