test: consolidate suites and remove redundant cases (#1459)

Regression tests were scattered across feature- and bug-specific files, and some suites repeated the same checks. Group tests by responsibility, isolate feature fixtures in test classes, and remove duplicate or obsolete cases.

The review covered all 127 collected test modules on main. This reduces them and removes or combines definitions:.

 No application code changes.

tests/test_emplan.py

@@ -1,9 +1,7 @@
-from typing import Optional
 
 import pytest
 
 from akkudoktoreos.core.emplan import (
-    BaseInstruction,
     CommodityQuantity,
     DDBCInstruction,
     EnergyManagementInstruction,
@@ -365,3 +363,38 @@ class TestEnergyManagementPlan:
 
         active_after = plan.get_active_instructions(exec_future)
         assert {i.resource_id for i in active_after} == {"dev-1"}
+
+
+class TestEnergyManagementPlanDST:
+    def test_repeated_hour_keeps_instruction_order_and_dispatch(self):
+        first = to_datetime("2026-10-25T02:45:00+02:00").in_timezone("Europe/Berlin")
+        second = to_datetime("2026-10-25T02:15:00+01:00").in_timezone("Europe/Berlin")
+        plan = EnergyManagementPlan(id="fold", generated_at=first, instructions=[])
+        later = FRBCInstruction(
+            resource_id="battery1",
+            actuator_id="battery1",
+            execution_time=second,
+            operation_mode_id="IDLE",
+            operation_mode_factor=1.0,
+        )
+        earlier = FRBCInstruction(
+            resource_id="battery1",
+            actuator_id="battery1",
+            execution_time=first,
+            operation_mode_id="GRID_SUPPORT_IMPORT",
+            operation_mode_factor=0.5,
+        )
+        plan.add_instruction(later)
+        plan.add_instruction(earlier)
+        assert [item.execution_time.timestamp() for item in plan.instructions] == [
+            first.timestamp(),
+            second.timestamp(),
+        ]
+        assert plan.valid_from is not None
+        assert plan.valid_from.timestamp() == first.timestamp()
+        assert plan.valid_until is None
+        between = to_datetime("2026-10-25T02:00:00+01:00").in_timezone("Europe/Berlin")
+        assert plan.get_active_instructions(between) == [earlier]
+        assert plan.get_next_instruction(between) == later
+        assert plan.get_active_instructions(second) == [later]
+        assert plan.get_next_instruction(second) is None