Initial commit: CI Agent competitive-intelligence monitoring app

FastAPI + Celery + Next.js + Postgres/Redis app with company monitoring,
source collection, LLM-based change analysis, enrichment, and account
security (Turnstile, escalating lockout, email verification).

apps/api/tests/unit/test_structured_diff.py

@@ -0,0 +1,26 @@
+from __future__ import annotations
+
+from app.change_detection.structured_diff import diff_item_sets
+
+
+def test_diff_item_sets_detects_additions_and_removals():
+    previous = ["https://x.com/a", "https://x.com/b"]
+    current = ["https://x.com/b", "https://x.com/c"]
+    diff = diff_item_sets(previous, current)
+    assert diff.added == ["https://x.com/c"]
+    assert diff.removed == ["https://x.com/a"]
+    assert diff.has_changes is True
+
+
+def test_diff_item_sets_no_change_when_identical():
+    items = ["https://x.com/a", "https://x.com/b"]
+    diff = diff_item_sets(items, list(items))
+    assert diff.added == []
+    assert diff.removed == []
+    assert diff.has_changes is False
+
+
+def test_diff_item_sets_handles_empty_previous():
+    diff = diff_item_sets([], ["https://x.com/a"])
+    assert diff.added == ["https://x.com/a"]
+    assert diff.removed == []