add eslint and prettier

backend/src/api.js

@@ -234,7 +234,7 @@ router.post("/games", asyncHandler(async (req, res) => {
 
         await conn.commit();
         res.status(201).json({ game: gameRow[0], players });
-    } catch (err) {
+    } catch (_err) {
         await conn.rollback();
         throw new ApiError(500, "Failed to create game");
     } finally {
@@ -299,7 +299,7 @@ router.post("/games/:id/players", asyncHandler(async (req, res) => {
 
         await conn.commit();
         res.status(201).json({ game: gameId, players });
-    } catch (err) {
+    } catch (_err) {
         await conn.rollback();
         throw new ApiError(500, "Failed to add player");
     } finally {
@@ -371,7 +371,7 @@ router.patch("/games/:id/lock", asyncHandler(async (req, res) => {
 
         await conn.commit();
         res.json({ message: "Game locked", turnOrder });
-    } catch (err) {
+    } catch (_err) {
         await conn.rollback();
         throw new ApiError(500, "Failed to lock game");
     } finally {
@@ -483,7 +483,7 @@ router.post("/games/:id/turns", asyncHandler(async (req, res) => {
 
         await conn.commit();
         res.status(201).json({ turnId: result.insertId, nextPlayer });
-    } catch (err) {
+    } catch (_err) {
         await conn.rollback();
         throw new ApiError(500, "Failed to record turn");
     } finally {