feat(three-stage-scan): add split-sink fixtures the regex scan misses

benchmarks/fixtures/split-sink-python/app.py

@@ -0,0 +1,11 @@
+"""Split-sink SQL injection: query is built, then executed on the next line."""
+from flask import Flask, request
+
+app = Flask(__name__)
+
+
+@app.get("/search")
+def search(db):
+    term = request.args["q"]
+    query = "select * from items where title like '%" + term + "%'"
+    return db.execute(query)  # CWE-89 split-sink: query built on prior line (regex blind spot)