M1: pure normalization engine + default seed

Infrastructure-free normalization engine in Core dispatching on MeterMode:
- Cumulative/Generation counters: register deltas, first-reading baseline (Haus 411,
  Auto 3755), meter swaps (water …861→2 reconciles to 12 via boundary registers OR an
  explicit amount override), counter resets, anomaly-guarded decreases.
- RuntimeCounter: Δhours × rate (fixed/empirical).
- ConsumableBalance: tank level-Δ + deliveries → consumption, cm→litre calibration;
  delivery-only rows before the first dipstick emit nothing.
- DirectDelta, and Virtual meters via a small safe arithmetic evaluator (Netz Einsparung
  = Haus − Netz, Eigenverbrauch = Erzeugung − Einsparung) — data-driven, not hardcoded.
- DatabaseSeeder: default energy types, cost categories, base settings (idempotent).

24 Core unit tests + 4 integration tests green.

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

tests/Core.Tests/CumulativeCounterNormalizerTests.cs

@@ -0,0 +1,105 @@
+using MeterVault.Core.Domain;
+using MeterVault.Core.Normalization;
+using static MeterVault.Core.Tests.TestData;
+
+namespace MeterVault.Core.Tests;
+
+public sealed class CumulativeCounterNormalizerTests
+{
+    private readonly INormalizationEngine _engine = NormalizationEngine.CreateDefault();
+
+    [Fact]
+    public void Straight_deltas_match_the_electricity_house_meter()
+    {
+        // Zähler Haus: Sept 0 → Okt 411 → Nov 1153 → Dez 1968 (SDD reference data).
+        var ctx = new NormalizationContext
+        {
+            Meter = new MeterConfig { MeterId = 1, Mode = MeterMode.CumulativeCounter, Unit = "kWh" },
+            Readings =
+            [
+                Reading(1, Month(2022, 9), 0),
+                Reading(1, Month(2022, 10), 411),
+                Reading(1, Month(2022, 11), 1153),
+                Reading(1, Month(2022, 12), 1968),
+            ],
+        };
+
+        var result = _engine.Normalize(ctx);
+
+        Assert.Equal([0d, 411d, 742d, 815d], result.Select(c => c.Amount));
+        Assert.All(result, c => Assert.Equal(ConsumptionKind.Consumption, c.Kind));
+    }
+
+    [Fact]
+    public void First_reading_books_the_full_register_against_a_zero_baseline()
+    {
+        // Zähler Auto appears mid-series: first reading 3755 → month-one consumption 3755.
+        var ctx = new NormalizationContext
+        {
+            Meter = new MeterConfig { MeterId = 3, Mode = MeterMode.CumulativeCounter, Unit = "kWh" },
+            Readings = [Reading(3, Month(2023, 5), 3755), Reading(3, Month(2023, 6), 3960)],
+        };
+
+        var result = _engine.Normalize(ctx);
+
+        Assert.Equal([3755d, 205d], result.Select(c => c.Amount));
+    }
+
+    [Fact]
+    public void Counter_reset_rebaselines_at_new_value()
+    {
+        var ctx = new NormalizationContext
+        {
+            Meter = new MeterConfig
+            {
+                MeterId = 1,
+                Mode = MeterMode.CumulativeCounter,
+                Unit = "kWh",
+                InitialBaseline = 90,
+            },
+            Readings =
+            [
+                Reading(1, Month(2023, 1), 100),
+                Reading(1, Month(2023, 2), 150),
+                Reading(1, Month(2023, 3), 30),
+                Reading(1, Month(2023, 4), 80),
+            ],
+            Events = [Reset(1, Month(2023, 3), newValue: 0)],
+        };
+
+        var result = _engine.Normalize(ctx);
+
+        Assert.Equal([10d, 50d, 30d, 50d], result.Select(c => c.Amount));
+    }
+
+    [Fact]
+    public void Unexplained_decrease_yields_zero_and_marks_quality()
+    {
+        var ctx = new NormalizationContext
+        {
+            Meter = new MeterConfig { MeterId = 1, Mode = MeterMode.CumulativeCounter, Unit = "kWh" },
+            Readings = [Reading(1, Month(2023, 1), 100), Reading(1, Month(2023, 2), 60)],
+        };
+
+        var result = _engine.Normalize(ctx);
+
+        Assert.Equal(0d, result[1].Amount);
+        Assert.Equal(ReadingQuality.Estimated, result[1].Quality);
+    }
+
+    [Fact]
+    public void Generation_meter_emits_generation_kind()
+    {
+        // Solar 2: Okt 0 → Nov 0 → ... → first real reading 7 in Feb.
+        var ctx = new NormalizationContext
+        {
+            Meter = new MeterConfig { MeterId = 5, Mode = MeterMode.GenerationCounter, Unit = "kWh" },
+            Readings = [Reading(5, Month(2023, 1), 0), Reading(5, Month(2023, 2), 7)],
+        };
+
+        var result = _engine.Normalize(ctx);
+
+        Assert.Equal([0d, 7d], result.Select(c => c.Amount));
+        Assert.All(result, c => Assert.Equal(ConsumptionKind.Generation, c.Kind));
+    }
+}