page the analysis run listings

Detection and segmentation run listings returned every run a project had ever
produced. Runs accumulate with every analysis while the panel only ever draws
the recent ones, so the response grew without bound for no benefit.

Both take limit and offset now and report total, limit, offset and truncated,
matching the result listings.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

backend/app/schemas/segmentation.py

@@ -71,7 +71,11 @@ class SegmentationRunRead(BaseModel):
 
 class SegmentationRunListResponse(BaseModel):
     items: list[SegmentationRunRead]
+    # ``total`` counts every run; ``items`` is the most recent page of them.
     total: int
+    limit: int | None = None
+    offset: int = 0
+    truncated: bool = False
 
 
 class SegmentationRead(BaseModel):