feat(costs): Pro-Nutzer-Kostenerfassung Stufe 1 (OpenRouter-Ist-Kosten)

CostMeter via ContextVars (app/core/costs.py, multitool-ready). Alle
OpenRouter-Calls (LLM, Sonar, Koreferenz, Fallback) senden usage:{include:true}
und buchen die Ist-Kosten je Kategorie (llm/web_search) — inkl. finalem
Streaming-usage-Chunk. cost_usage-Tabelle (user/day/category) + Store-Methoden;
ws.py/chat.py start_meter pro Turn + persist_costs. Statistik: Spalten
"Kosten (Monat)" + "Ø/Anfrage" + Gesamt. Live: 1 Such-Turn ~ $0,0052
(web_search dominiert, LLM ~ $0,00007). Tests: 318.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/store.py

@@ -128,6 +128,14 @@ class Store(ABC):
     def add_web_search_usage(self, user_id: str, n: int = 1, day: str | None = None) -> int:
         """Zaehlt n Web-Suchen dazu und liefert die neue Tages-Zahl."""
 
+    @abstractmethod
+    def add_cost_usage(self, user_id: str, category: str, usd: float, day: str | None = None) -> None:
+        """Bucht Kosten (USD) auf Nutzer/Tag/Kategorie."""
+
+    @abstractmethod
+    def cost_for_day(self, user_id: str, day: str | None = None) -> float:
+        """Summe der Kosten (USD) des Nutzers am Tag (Default: heute, UTC)."""
+
     @abstractmethod
     def delete_user(self, user_id: str) -> bool:
         """Loescht einen Nutzer und alle seine Daten (Sessions, Nachrichten, Erinnerungen,
@@ -243,6 +251,13 @@ class SQLiteStore(Store):
                     count INTEGER NOT NULL DEFAULT 0,
                     PRIMARY KEY (user_id, day)
                 );
+                CREATE TABLE IF NOT EXISTS cost_usage (
+                    user_id TEXT NOT NULL,
+                    day TEXT NOT NULL,
+                    category TEXT NOT NULL,
+                    amount_usd REAL NOT NULL DEFAULT 0,
+                    PRIMARY KEY (user_id, day, category)
+                );
                 CREATE TABLE IF NOT EXISTS emergency_events (
                     id INTEGER PRIMARY KEY AUTOINCREMENT,
                     user_id TEXT NOT NULL,
@@ -517,6 +532,29 @@ class SQLiteStore(Store):
             ).fetchone()
         return int(row["count"])
 
+    def add_cost_usage(self, user_id: str, category: str, usd: float,
+                       day: str | None = None) -> None:
+        if not usd or usd <= 0:
+            return
+        day = day or self._today()
+        with self._connect() as conn:
+            conn.execute(
+                "INSERT INTO cost_usage (user_id, day, category, amount_usd) VALUES (?, ?, ?, ?)"
+                " ON CONFLICT(user_id, day, category) DO UPDATE SET"
+                " amount_usd = amount_usd + excluded.amount_usd",
+                (user_id, day, category, float(usd)),
+            )
+
+    def cost_for_day(self, user_id: str, day: str | None = None) -> float:
+        day = day or self._today()
+        with self._connect() as conn:
+            row = conn.execute(
+                "SELECT COALESCE(SUM(amount_usd), 0) AS s FROM cost_usage"
+                " WHERE user_id = ? AND day = ?",
+                (user_id, day),
+            ).fetchone()
+        return float(row["s"]) if row else 0.0
+
     def delete_user(self, user_id: str) -> bool:
         if user_id == ANONYMOUS_USER_ID:
             raise ValueError("Der anonyme Nutzer kann nicht geloescht werden.")
@@ -532,6 +570,7 @@ class SQLiteStore(Store):
             conn.execute("DELETE FROM memories WHERE user_id = ?", (user_id,))
             conn.execute("DELETE FROM usage WHERE user_id = ?", (user_id,))
             conn.execute("DELETE FROM web_search_usage WHERE user_id = ?", (user_id,))
+            conn.execute("DELETE FROM cost_usage WHERE user_id = ?", (user_id,))
             conn.execute("DELETE FROM users WHERE id = ?", (user_id,))
         return True
 
@@ -639,15 +678,21 @@ class SQLiteStore(Store):
         return [dict(r) for r in rows]
 
     def get_all_usage(self) -> list[dict]:
+        month = datetime.now(timezone.utc).strftime("%Y-%m") + "-%"
         with self._connect() as conn:
             rows = conn.execute(
                 "SELECT u.user_id, COALESCE(usr.display_name, u.user_id) AS display_name,"
                 " SUM(u.requests) AS total_requests, SUM(u.units) AS total_units,"
                 " MAX(u.day) AS last_active,"
                 " COALESCE((SELECT SUM(w.count) FROM web_search_usage w"
-                "           WHERE w.user_id = u.user_id), 0) AS total_web_searches"
+                "           WHERE w.user_id = u.user_id), 0) AS total_web_searches,"
+                " COALESCE((SELECT SUM(c.amount_usd) FROM cost_usage c"
+                "           WHERE c.user_id = u.user_id AND c.day LIKE ?), 0) AS month_cost_usd,"
+                " COALESCE((SELECT SUM(uu.requests) FROM usage uu"
+                "           WHERE uu.user_id = u.user_id AND uu.day LIKE ?), 0) AS month_requests"
                 " FROM usage u LEFT JOIN users usr ON usr.id = u.user_id"
                 " GROUP BY u.user_id ORDER BY total_requests DESC",
+                (month, month),
             ).fetchall()
         return [dict(r) for r in rows]