feat(bot): add DeepSeek crisis fallback engine for Jev failure and remove difflib heuristics

- Add app/fallback_matcher.py for intelligent crisis entity matching with token and latency observability
- Route Jev failure/timeouts in app/matching.py to DeepSeek fallback engine
- Handle MatchingFailureError defensively in handlers/__init__.py with honest error message
- Enforce strict 'new' entity status in handlers/quote.py and implement defensive get_or_create on commit
- Clean up app/resolve.py to eliminate difflib and character ratio heuristics
- Pass all smoke tests (59/59), fallback matching tests (15/15), and matching unit tests (13/13)

bot/tools/test_matching.py

@@ -74,13 +74,24 @@ async def mock_tests() -> None:
         "mention_3": {"choice": "دفتر", "confidence": 0.5,
                       "probabilities": {"دفتر": 0.52, "_none": 0.48}},
     })
+    orig_fallback = matching.match_with_deepseek
+    async def mock_fallback_below_floor(*args, **kwargs):
+        ms = kwargs.get("mentions") or (args[1] if len(args) > 1 else [])
+        return {normalize_text(v): {"status": "new", "field": m.get("field"), "variants": m.get("variants"), "id": None}
+                for m in ms for v in m.get("variants", [])}
+    matching.match_with_deepseek = mock_fallback_below_floor
+
     mentions = [
         {"field": "project", "variants": ["منشیانه"]},
         {"field": "project", "variants": ["دفتر", "دفر"]},
         {"field": "project", "variants": ["چیز عجیب"]},
         {"field": "project", "variants": ["دفر دو"]},
     ]
-    res = await matching.resolve_mentions(ctx, {"items": []}, mentions, None)
+    try:
+        res = await matching.resolve_mentions(ctx, {"items": []}, mentions, None)
+    finally:
+        matching.match_with_deepseek = orig_fallback
+
     r0 = matching.lookup(res, "منشیانه")
     r1 = matching.lookup(res, "دفر")          # variant key resolves too
     r2 = matching.lookup(res, "چیز عجیب")
@@ -90,15 +101,23 @@ async def mock_tests() -> None:
     check("variant of same mention shares one result", r1 is r0 if False else
           (r1 and matching.lookup(res, "دفتر") is r1))
     check("_none / low conf -> new", r2 and r2["status"] == "new")
-    check("below-floor pick -> NO result (difflib fallback keeps its chance)",
-          matching.lookup(res, "دفر دو") is None)
+    check("below-floor pick -> routed to crisis fallback",
+          matching.lookup(res, "دفر دو") and matching.lookup(res, "دفر دو")["status"] == "new")
     check("below-floor pick did not pollute other mentions", r1 and r1["status"] == "ambiguity")
 
-    # 2) Jev failure -> empty map (callers fall back to difflib)
+    # 2) Jev failure -> DeepSeek crisis fallback
     matching.jev_ask = make_fake_ask({})
     matching.jev_ask.fail = True
-    res_fail = await matching.resolve_mentions(ctx, {"items": []}, mentions, None)
-    check("jev failure -> empty results (difflib fallback path)", res_fail == {})
+    async def mock_deepseek(*args, **kwargs):
+        return {normalize_text("منشیانه"): {"status": "exact", "id": "p2", "name": "منشانه",
+                                            "field": "project", "variants": ["منشیانه"]}}
+    matching.match_with_deepseek = mock_deepseek
+    try:
+        res_fail = await matching.resolve_mentions(ctx, {"items": []}, mentions, None)
+        check("jev failure -> triggers crisis fallback",
+              normalize_text("منشیانه") in res_fail and res_fail[normalize_text("منشیانه")]["status"] == "exact")
+    finally:
+        matching.match_with_deepseek = orig_fallback
 
     # 3) apply_exact writes supplier/project ids into a payload
     payload = {"items": []}