Add CallerIdentity dataclass and batch JSON parser

tests/test_caller_gen.py

@@ -0,0 +1,37 @@
+import pytest
+from backend.services.caller_gen import CallerIdentity, parse_batch_response
+
+SAMPLE_JSON = """
+{
+  "callers": [
+    {
+      "name": "Danny Ortega",
+      "age": 47,
+      "voice_suggestion": "Marcus",
+      "location": "Silver City, NM",
+      "identity": "A plumber who inherited his uncle's taxidermy shop...",
+      "situation": "He's been getting calls from people...",
+      "reason_calling": "Someone left a note in his mailbox tonight...",
+      "opening_line": "Luke, I need to ask you something weird.",
+      "secret_want": "Permission to just throw it all away",
+      "specific_details": ["the elk head in the basement", "the note said 'she forgot'", "his uncle's Rolodex"],
+      "emotional_register": "quietly unsettled, trying to sound casual"
+    }
+  ]
+}
+"""
+
+
+def test_parse_batch_response_returns_caller_list():
+    callers = parse_batch_response(SAMPLE_JSON)
+    assert len(callers) == 1
+    assert callers[0].name == "Danny Ortega"
+    assert callers[0].age == 47
+    assert "taxidermy" in callers[0].identity
+    assert len(callers[0].specific_details) == 3
+
+
+def test_parse_batch_response_rejects_missing_fields():
+    bad = '{"callers": [{"name": "Jim"}]}'
+    with pytest.raises(ValueError, match="missing"):
+        parse_batch_response(bad)