DSMR hardening: restart-free config + decouple from telegram id

Config hot-reload (no restart):
- MqttManager.unsubscribe(); apply_dsmr_subscription(settings) re-applies the
  DSMR subscription (subscribe/unsubscribe/topic-change, fresh snapshot so the
  sample interval also takes effect).
- Called from lifespan AND PUT /api/config, so toggling DSMR ingest in the UI
  takes effect immediately without restarting the app.

Decouple ingest from the DSMR telegram id (overflows / resets to zero):
- Migration 20260624_12: drop UNIQUE(source_id), make recorded_at UNIQUE.
- Idempotency now keys on recorded_at (telegram timestamp); the table's own
  autoincrement PK is the stable identity. source_id kept only as a reference.
- Regression test: colliding telegram ids no longer drop new data.

tests/test_energy_models.py

@@ -117,21 +117,21 @@ def test_dsmr_reading_columns(energy_db):
     assert "payload" in columns and not columns["payload"]["nullable"]
 
 
-def test_dsmr_reading_source_id_unique(energy_db):
-    """dsmr_reading.source_id must have a unique constraint."""
+def test_dsmr_reading_recorded_at_unique(energy_db):
+    """dsmr_reading.recorded_at is the UNIQUE de-dup key (telegram-id-independent)."""
     inspector = inspect(energy_db)
     unique_constraints = inspector.get_unique_constraints("dsmr_reading")
     unique_cols = [col for uc in unique_constraints for col in uc["column_names"]]
-    assert "source_id" in unique_cols, "source_id must have a unique constraint"
+    assert "recorded_at" in unique_cols, "recorded_at must have a unique constraint"
 
 
-def test_dsmr_reading_recorded_at_index(energy_db):
-    """dsmr_reading.recorded_at must have an index."""
+def test_dsmr_reading_source_id_not_unique(energy_db):
+    """dsmr_reading.source_id (telegram id) must NOT be unique — it overflows/resets,
+    so it is kept only as a reference value and never relied on for dedup."""
     inspector = inspect(energy_db)
-    indexes = {idx["name"]: idx for idx in inspector.get_indexes("dsmr_reading")}
-    assert "ix_dsmr_reading_recorded_at" in indexes, (
-        "ix_dsmr_reading_recorded_at missing from dsmr_reading"
-    )
+    unique_constraints = inspector.get_unique_constraints("dsmr_reading")
+    unique_cols = [col for uc in unique_constraints for col in uc["column_names"]]
+    assert "source_id" not in unique_cols, "source_id must NOT have a unique constraint"
 
 
 def test_energy_contract_columns(energy_db):
@@ -268,6 +268,40 @@ def test_downgrade_removes_energy_tables(tmp_path: Path):
     engine.dispose()
 
 
+def test_dsmr_decouple_migration_downgrade_restores_source_id_unique(tmp_path: Path):
+    """Downgrading the telegram-id-decouple migration to 20260623_11 must restore the
+    original constraints: source_id UNIQUE, recorded_at non-unique index."""
+    db_path = tmp_path / "dsmr_decouple_downgrade.db"
+    db_url = f"sqlite:///{db_path}"
+    alembic_cfg = _make_app_alembic_config(db_url)
+
+    command.upgrade(alembic_cfg, "head")
+
+    # At head: recorded_at is unique, source_id is not.
+    engine = create_engine(db_url, connect_args={"check_same_thread": False})
+    inspector = inspect(engine)
+    head_unique = [
+        c for uc in inspector.get_unique_constraints("dsmr_reading") for c in uc["column_names"]
+    ]
+    assert "recorded_at" in head_unique
+    assert "source_id" not in head_unique
+    engine.dispose()
+
+    # Downgrade just this migration.
+    command.downgrade(alembic_cfg, "20260623_11_energy_tables")
+
+    engine = create_engine(db_url, connect_args={"check_same_thread": False})
+    inspector = inspect(engine)
+    pre_unique = [
+        c for uc in inspector.get_unique_constraints("dsmr_reading") for c in uc["column_names"]
+    ]
+    assert "source_id" in pre_unique, "source_id unique must be restored on downgrade"
+    assert "recorded_at" not in pre_unique
+    index_names = {idx["name"] for idx in inspector.get_indexes("dsmr_reading")}
+    assert "ix_dsmr_reading_recorded_at" in index_names
+    engine.dispose()
+
+
 # ---------------------------------------------------------------------------
 # 2. ORM metadata checks (Base.metadata)
 # ---------------------------------------------------------------------------
@@ -332,11 +366,12 @@ def test_energy_cost_period_fk_ondelete_restrict():
     )
 
 
-def test_dsmr_reading_source_id_unique_in_metadata():
-    """DsmrReading.source_id must be declared unique in ORM metadata."""
+def test_dsmr_reading_recorded_at_unique_in_metadata():
+    """DsmrReading.recorded_at must be the unique de-dup key in ORM metadata,
+    and source_id must NOT be unique (decoupled from the telegram id)."""
     table = Base.metadata.tables["dsmr_reading"]
-    col = table.columns["source_id"]
-    assert col.unique, "source_id must be declared unique"
+    assert table.columns["recorded_at"].unique, "recorded_at must be declared unique"
+    assert not table.columns["source_id"].unique, "source_id must NOT be unique"
 
 
 def test_tibber_price_starts_at_unique_in_metadata():