Implemented the feedback foundation.

src/fgai/feedback.py

@@ -0,0 +1,27 @@
+from __future__ import annotations
+
+import json
+import time
+from pathlib import Path
+
+
+class FeedbackStore:
+    def __init__(self, path: str = "state/signalscope-feedback.json") -> None:
+        self.path = Path(path)
+
+    def entries(self) -> list[dict[str, object]]:
+        try:
+            items = json.loads(self.path.read_text(encoding="utf-8"))
+        except (FileNotFoundError, json.JSONDecodeError):
+            items = []
+        now = int(time.time())
+        return [item for item in items if not item.get("expires_at") or int(item["expires_at"]) > now]
+
+    def add(self, item: dict[str, object]) -> dict[str, object]:
+        status = str(item.get("status", "")).lower()
+        if status not in {"false_positive", "expected", "confirmed"}:
+            raise ValueError("invalid feedback status")
+        entry = {"stream_id": str(item.get("stream_id", "")), "entity": str(item.get("entity", "")), "field": str(item.get("field", "")), "status": status, "note": str(item.get("note", "")), "created_at": int(time.time()), "expires_at": int(item.get("expires_at", 0) or 0)}
+        entries = [value for value in self.entries() if (value.get("stream_id"), value.get("entity"), value.get("field")) != (entry["stream_id"], entry["entity"], entry["field"])]
+        entries.append(entry); self.path.parent.mkdir(parents=True, exist_ok=True); self.path.write_text(json.dumps(entries, indent=2), encoding="utf-8")
+        return entry