Similar versions: surface-overlap metric + endpoint + UI panel

Ranks catalogued engine versions by how much of their CMC_* surface they share,
which (unlike a binary fuzzy hash) stays meaningful across compilers — the golden
pair PIKLIB8/MSVC6 vs bloomoodll/MSVC8 scores 85%.

- similarity.py: jaccard, surface_similarity (per-axis + pooled overall),
  fuzzy_similarity (ssdeep via ppdeep, secondary signal)
- service.similar_snapshots + GET /snapshots/{id}/similar?min=N (SimilarHit)
- UI: "Podobne wersje" panel in the snapshot browser (overlap bar + ⇄ diff)
- tests: 6 new (jaccard, identical/disjoint, golden pair 0<x<100, fuzzy,
  endpoint + min filter) -> 28/28

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

ams/api/schemas.py

@@ -43,6 +43,13 @@ class GameDetail(GameOut):
     snapshots: list[SnapshotOut] = []
 
 
+class SimilarHit(BaseModel):
+    snapshot: SnapshotOut
+    overall: int            # pooled surface-overlap score 0–100
+    fuzzy: int | None       # ssdeep similarity of the raw binary, when available
+    axes: dict              # per-axis {shared, only_a, only_b, score}
+
+
 class JobOut(BaseModel):
     model_config = ConfigDict(from_attributes=True)
     id: int