Hide + archive stale listings (old jobs, expired shifts)

- ListingPolicy.JobFreshnessDays=30: public /Jobs and home hide jobs older than the cutoff (shifts already require Date>=today)
- ListingArchiver flips stale Open→Expired: shifts past their date, jobs older than the cutoff. Runs at startup and on every IngestionWorker cycle (independent of ingestion being enabled)
- Verified: backdated job dropped off /Jobs (6→5) and was archived to Expired on the sweep

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/JobsMedical.Web/Program.cs

@@ -44,6 +44,7 @@ builder.Services.AddSingleton<JobsMedical.Web.Services.Scraping.IListingSource,
     JobsMedical.Web.Services.Scraping.DivarListingSource>();
 builder.Services.AddSingleton<JobsMedical.Web.Services.Scraping.IListingSource,
     JobsMedical.Web.Services.Scraping.MedjobsListingSource>();
+builder.Services.AddScoped<JobsMedical.Web.Services.Scraping.ListingArchiver>();
 builder.Services.AddScoped<JobsMedical.Web.Services.Scraping.IngestionService>();
 builder.Services.AddHostedService<JobsMedical.Web.Services.Scraping.IngestionWorker>();
 
@@ -74,6 +75,10 @@ using (var scope = app.Services.CreateScope())
     db.Database.Migrate();
     // Production seeds reference data only (no demo facilities/shifts); dev seeds the full board.
     await SeedData.EnsureSeededAsync(db, app.Environment.IsDevelopment());
+    // Archive any listings that went stale while the app was down.
+    await scope.ServiceProvider
+        .GetRequiredService<JobsMedical.Web.Services.Scraping.ListingArchiver>()
+        .ArchiveStaleAsync();
 }
 
 // Configure the HTTP request pipeline.