feat: trackeo de coste por llamada Claude — tabla api_usage + /costs

src/db/database.py

@@ -88,6 +88,17 @@ CREATE INDEX IF NOT EXISTS idx_sources_session ON sources(session_id);
 CREATE INDEX IF NOT EXISTS idx_chunks_session ON chunks(session_id);
 CREATE INDEX IF NOT EXISTS idx_chunks_quality ON chunks(session_id, quality_score DESC);
 CREATE INDEX IF NOT EXISTS idx_source_contents ON source_contents(source_id);
+
+CREATE TABLE IF NOT EXISTS api_usage (
+    id INTEGER PRIMARY KEY AUTOINCREMENT,
+    session_id INTEGER REFERENCES research_sessions(id),
+    call_type TEXT NOT NULL,
+    model TEXT NOT NULL,
+    input_tokens INTEGER NOT NULL,
+    output_tokens INTEGER NOT NULL,
+    cost_usd REAL NOT NULL,
+    created_at REAL NOT NULL
+);
 """
 
 
@@ -271,6 +282,43 @@ class ResearchDB:
         rows = await cursor.fetchall()
         return [dict(r) for r in rows]
 
+    # --- API Usage ---
+
+    async def log_api_call(self, session_id, call_type: str, model: str,
+                            input_tokens: int, output_tokens: int):
+        # Precios Claude Haiku (claude-haiku-4-5):
+        # input: $0.80 / 1M tokens  output: $4.00 / 1M tokens
+        cost = (input_tokens * 0.80 + output_tokens * 4.00) / 1_000_000
+        await self.db.execute(
+            """INSERT INTO api_usage
+               (session_id, call_type, model, input_tokens, output_tokens, cost_usd, created_at)
+               VALUES (?,?,?,?,?,?,?)""",
+            (session_id, call_type, model, input_tokens, output_tokens, cost, time.time())
+        )
+        await self.db.commit()
+
+    async def get_usage_stats(self, session_id: int) -> list[dict]:
+        cursor = await self.db.execute(
+            """SELECT call_type,
+                      COUNT(*) as calls,
+                      SUM(input_tokens + output_tokens) as total_tokens,
+                      SUM(cost_usd) as total_cost
+               FROM api_usage WHERE session_id = ?
+               GROUP BY call_type""",
+            (session_id,)
+        )
+        rows = await cursor.fetchall()
+        return [dict(r) for r in rows]
+
+    async def get_total_usage_stats(self) -> dict:
+        cursor = await self.db.execute(
+            """SELECT COUNT(DISTINCT session_id) as sessions,
+                      SUM(cost_usd) as total_cost
+               FROM api_usage"""
+        )
+        row = await cursor.fetchone()
+        return dict(row) if row else {"sessions": 0, "total_cost": 0}
+
     # --- Maintenance ---
 
     async def purge_old_sessions(self, max_age_days: int = 30) -> dict: