feat: add return to service workflow

backend/app/repairs/exceptions.py

@@ -62,5 +62,48 @@ class RepairActorRequired(RepairError):
         super().__init__("An authenticated actor is required to begin repair")
 
 
+class RepairCompletionActorRequired(RepairError):
+    """Raised when Return to Service lacks an authenticated actor."""
+
+    def __init__(self):
+        super().__init__(
+            "An authenticated actor is required to return a miner to service"
+        )
+
+
+class RepairNotActive(RepairConflict):
+    """Raised when a repair is no longer active."""
+
+    def __init__(self, repair_id: object, repair_status: object):
+        self.repair_id = repair_id
+        self.repair_status = repair_status
+        super().__init__(
+            f"Repair is not active: {repair_id} ({repair_status})"
+        )
+
+
+class RepairMinerNotInRepair(RepairConflict):
+    """Raised when a repair's miner has already left repair lifecycle."""
+
+    def __init__(self, miner_id: object, lifecycle_status: object):
+        self.miner_id = miner_id
+        self.lifecycle_status = lifecycle_status
+        super().__init__(
+            "Miner is not in repair lifecycle: "
+            f"{miner_id} ({lifecycle_status})"
+        )
+
+
+class RepairActiveMismatch(RepairConflict):
+    """Raised when the requested repair is not the miner's active repair."""
+
+    def __init__(self, repair_id: object, miner_id: object):
+        self.repair_id = repair_id
+        self.miner_id = miner_id
+        super().__init__(
+            f"Repair is not the active repair for miner: {repair_id}"
+        )
+
+
 class RepairPersistenceError(RepairError):
     """Raised when a required repair persistence operation fails."""