Polish/audit: fix bugs found by 3 subsystem audits

Correctness/data:
- Fix demo cost double-count: reference importer no longer imports the Kosten Strom/Wasser
  columns for categories that are metered (only Heizung), so Wasser rollup is 70€ not 140€.
- Spurious-decrease guard: only a reset/swap in the window (prevReading, thisReading] explains
  a decrease — an old historical reset no longer permanently disables the guard.
- Gate swap auto-detection on MappingProfile.DetectCumulativeSwaps (flag was ignored).
- Prorate basePrice by bucket length (day/month/year); guard virtual expressions against NaN/Inf.

Concurrency/infra:
- Blazor: register a DbContextFactory; CostService/DashboardService and the read pages now use
  short-lived per-operation contexts (no shared circuit DbContext); guard Trends re-entrancy.
- /events: wrap event insert + consumption recompute in one transaction (atomic); 404 (not 500)
  on unknown meter.
- MQTT worker: subscribe to newly-added topics on each tick; move client cleanup into finally.
- Migrations: CREATE MATERIALIZED VIEW IF NOT EXISTS + if_not_exists on CAgg/compression/
  hypertable calls (re-run-safe after a mid-migration crash).
- HA worker: prune stale poll-schedule entries; export: null dangling ImportBatchIds on restore.

API/security:
- API fail-closed by default: with no keys and AllowAnonymousApi off, /api/v1 returns 401
  (protects /export and /import). New MeterVault:AllowAnonymousApi opt-in.
- Cap /readings batch at 5000; report ignored (unknown-meter) count; enums as strings in JSON.

+4 regression tests (guard window, API closed, /events 404, no demo double-count). 98 tests
green; Docker deploy re-verified healthy with the API fail-closed.

Claude-Session: https://claude.ai/code/session_01WujdMtMJPbxDpDnMeK22rr

tests/Integration.Tests/ApiTests.cs

@@ -52,6 +52,37 @@ public sealed class ApiTests(TimescaleFixture fx)
         }
     }
 
+    private sealed record EventPush(int MeterId, DateTimeOffset Time, string Type,
+        double? Amount, double? PrevValue, double? NewValue, string? Unit, string? Notes);
+
+    [Fact]
+    public async Task Api_is_closed_when_no_keys_are_configured()
+    {
+        using var factory = new MeterVaultAppFactory(fx.ConnectionString, configureApiKey: false);
+        using var client = factory.CreateClient();
+
+        var response = await client.PostAsJsonAsync("/api/v1/readings",
+            new[] { new ReadingPush(1, DateTimeOffset.UtcNow, 1) });
+
+        Assert.Equal(HttpStatusCode.Unauthorized, response.StatusCode);
+    }
+
+    [Fact]
+    public async Task Events_for_a_missing_meter_return_404_not_500()
+    {
+        using var factory = new MeterVaultAppFactory(fx.ConnectionString);
+        using var client = factory.CreateClient();
+
+        using var request = new HttpRequestMessage(HttpMethod.Post, "/api/v1/events")
+        {
+            Content = JsonContent.Create(new EventPush(999999, DateTimeOffset.UtcNow, "Delivery", 100, null, null, "L", null)),
+        };
+        request.Headers.Add("X-Api-Key", MeterVaultAppFactory.ApiKey);
+        var response = await client.SendAsync(request);
+
+        Assert.Equal(HttpStatusCode.NotFound, response.StatusCode);
+    }
+
     [Fact]
     public async Task Meters_endpoint_and_swagger_are_available()
     {

tests/Integration.Tests/Costing/CostReconciliationTests.cs

@@ -36,7 +36,7 @@ public sealed class CostReconciliationTests(TimescaleFixture fx)
         });
         await db.SaveChangesAsync();
 
-        var costs = await new CostService(db).GetMeterCostsAsync(meterId, From, To);
+        var costs = await new CostService(fx).GetMeterCostsAsync(meterId, From, To);
         var computed = costs.ToDictionary(c => c.Period, c => c.Cost);
         var oracle = OracleByMonth(ReadRows(Water), dateColumn: 0, valueColumn: 4, firstDataRow: 1); // Kosten
 
@@ -64,7 +64,7 @@ public sealed class CostReconciliationTests(TimescaleFixture fx)
         db.CostCategoryMembers.Add(new CostCategoryMember { CategoryId = wasserCategory.Id, MeterId = meterId });
         await db.SaveChangesAsync();
 
-        var rollup = await new CostService(db).GetCategoryCostsAsync(wasserCategory.Id, From, To);
+        var rollup = await new CostService(fx).GetCategoryCostsAsync(wasserCategory.Id, From, To);
         var dec2022 = rollup.Single(r => r.Period == new DateOnly(2022, 12, 1));
 
         Assert.Equal(70d, dec2022.Cost, 2); // Dez 2022: 14 m³ × 5,00 €

tests/Integration.Tests/DashboardRenderTests.cs

@@ -1,3 +1,4 @@
+using MeterVault.Infrastructure.Costing;
 using MeterVault.Infrastructure.Import;
 using MeterVault.Infrastructure.Persistence;
 using Microsoft.EntityFrameworkCore;
@@ -31,6 +32,15 @@ public sealed class DashboardRenderTests(TimescaleFixture fx)
                 Assert.Contains(await db.Meters.Select(m => m.Name).ToListAsync(), n => n == "Zähler Haus");
                 Assert.True(await db.Meters.CountAsync() >= 8);
                 Assert.True(await db.Consumption.AnyAsync());
+
+                // Regression (audit): Wasser is metered (water tariff), the Kosten Wasser column is
+                // NOT imported, so the category is not double-counted — Dez 2022 = 14 m³ × 5 € = 70 €.
+                var wasser = await db.CostCategories.FirstAsync(c => c.Name == "Wasser");
+                var rollup = await new CostService(fx).GetCategoryCostsAsync(
+                    wasser.Id,
+                    new DateTimeOffset(2022, 12, 1, 0, 0, 0, TimeSpan.Zero),
+                    new DateTimeOffset(2023, 1, 1, 0, 0, 0, TimeSpan.Zero));
+                Assert.Equal(70d, rollup.Sum(r => r.Cost), 1);
             }
 
             using var client = factory.CreateClient();

tests/Integration.Tests/Ingestion/IngestionServiceTests.cs

@@ -49,6 +49,28 @@ public sealed class IngestionServiceTests(TimescaleFixture fx)
         await CleanupAsync(db, meterId);
     }
 
+    [Fact]
+    public async Task Old_reset_does_not_permanently_disable_the_decrease_guard()
+    {
+        await using var db = fx.CreateContext();
+        var (meterId, sourceId) = await SetupAsync(db, MeterMode.CumulativeCounter);
+        var service = new IngestionService(db);
+
+        // A reset early on explains an early decrease...
+        await service.IngestAsync(sourceId, T0, 100);
+        db.MeterEvents.Add(new MeterEvent { MeterId = meterId, Time = T0.AddMinutes(10), EventType = MeterEventType.CounterReset, NewValue = 0 });
+        await db.SaveChangesAsync();
+        Assert.Equal(IngestionOutcome.Written, await service.IngestAsync(sourceId, T0.AddMinutes(20), 30));
+        await service.IngestAsync(sourceId, T0.AddHours(1), 200);
+
+        // ...but a later spurious decrease with NO event in its window must still be rejected.
+        var outcome = await service.IngestAsync(sourceId, T0.AddHours(2), 150);
+
+        Assert.Equal(IngestionOutcome.RejectedDecrease, outcome);
+
+        await CleanupAsync(db, meterId);
+    }
+
     [Fact]
     public async Task Allows_decrease_when_a_swap_event_explains_it()
     {

tests/Integration.Tests/MeterVaultAppFactory.cs

@@ -7,7 +7,7 @@ namespace MeterVault.Integration.Tests;
 /// Boots the real ASP.NET Core app in-memory against the shared Timescale container.
 /// Migrations are already applied by <see cref="TimescaleFixture"/>, so startup migration is off.
 /// </summary>
-public sealed class MeterVaultAppFactory(string connectionString) : WebApplicationFactory<Program>
+public sealed class MeterVaultAppFactory(string connectionString, bool configureApiKey = true) : WebApplicationFactory<Program>
 {
     public const string ApiKey = "test-api-key";
 
@@ -17,6 +17,9 @@ public sealed class MeterVaultAppFactory(string connectionString) : WebApplicati
         builder.UseSetting("ConnectionStrings:Default", connectionString);
         builder.UseSetting("MeterVault:RunMigrationsAtStartup", "false");
         builder.UseSetting("MeterVault:EnableLiveIngestion", "false");
-        builder.UseSetting("MeterVault:ApiKeys:0", ApiKey);
+        if (configureApiKey)
+        {
+            builder.UseSetting("MeterVault:ApiKeys:0", ApiKey);
+        }
     }
 }

tests/Integration.Tests/TimescaleFixture.cs

@@ -10,7 +10,7 @@ namespace MeterVault.Integration.Tests;
 /// The image tag is pinned: the compression DDL (add_compression_policy) was renamed toward
 /// add_columnstore_policy in newer Timescale, so a floating tag would risk breaking migrations.
 /// </summary>
-public sealed class TimescaleFixture : IAsyncLifetime
+public sealed class TimescaleFixture : IAsyncLifetime, IDbContextFactory<MeterVaultDbContext>
 {
     private readonly PostgreSqlContainer _db = new PostgreSqlBuilder("timescale/timescaledb:2.17.2-pg16")
         .WithDatabase("metervault")
@@ -30,6 +30,9 @@ public sealed class TimescaleFixture : IAsyncLifetime
         return new MeterVaultDbContext(options);
     }
 
+    /// <summary>Lets tests construct services that take an <see cref="IDbContextFactory{TContext}"/>.</summary>
+    public MeterVaultDbContext CreateDbContext() => CreateContext();
+
     public async Task InitializeAsync()
     {
         await _db.StartAsync();