M8-T06: add meter source management API

app/schemas/meter.py

@@ -49,10 +49,21 @@ class MeterResponse(BaseModel):
     reason: str
     note: str | None
     created_at: datetime
+    bindings: list["MeterBindingSummary"] = Field(default_factory=list)
 
     model_config = {"from_attributes": True}
 
 
+class MeterBindingSummary(BaseModel):
+    """Stable, non-sensitive binding identity embedded in meter responses."""
+
+    uuid: str
+    source_channel_uuid: str
+    source_uuid: str
+    started_at: datetime
+    ended_at: datetime | None
+
+
 class MeterListResponse(BaseModel):
     """Response schema for GET /api/energy/meters.
 
@@ -107,6 +118,12 @@ class MeterDeclareRequest(BaseModel):
         max_length=32,
         description="Energy commodity this meter measures.  Defaults to 'electricity'.",
     )
+    source_channel_uuid: str | None = Field(
+        default=None,
+        min_length=1,
+        max_length=36,
+        description="Optional compatible source channel to bind atomically to this meter.",
+    )
 
 
 class MeterPatchRequest(BaseModel):