fix(social): robot blocks

Blocking an auto-match opponent who is secretly a pooled robot is recorded  instead in a separate `robot_blocks` table.

Now blocking behaves the same in that game (struck name, hidden composer) and lists the blocked opponent under the name you saw, but is recorded only against that game — the disguise holds, the shared robot is never globally blocked, and the matchmaker keeps pairing you with robots (so you can never block yourself out of opponents).

- the shared robot account is never put in `blocks`
- the matchmaker keeps it free and it is not blocked under its other per-game names
- the blocked list and the in-game card still show it by joining that table; an unblock deletes the row

gateway/internal/backendclient/api_social.go

@@ -42,9 +42,20 @@ type RedeemResultResp struct {
 	Friend AccountRefResp `json:"friend"`
 }
 
-// BlockListResp is the accounts the caller has blocked.
+// BlockListResp is the accounts the caller has blocked, plus the per-game disguised-robot
+// blocks (not real accounts).
 type BlockListResp struct {
 	Blocked []AccountRefResp `json:"blocked"`
+	Robots  []RobotBlockResp `json:"robots"`
+}
+
+// RobotBlockResp is one per-game disguised-robot block: the row id (to unblock it), the game
+// name the player saw, and the game + seat it was blocked in.
+type RobotBlockResp struct {
+	ID          string `json:"id"`
+	DisplayName string `json:"display_name"`
+	GameID      string `json:"game_id"`
+	Seat        int    `json:"seat"`
 }
 
 // StatsResp is a durable account's lifetime statistics. BestMoves breaks the best move
@@ -188,10 +199,11 @@ func (c *Client) RedeemFriendCode(ctx context.Context, userID, code string) (Red
 
 // --- blocks ---
 
-// Block blocks an account.
-func (c *Client) Block(ctx context.Context, userID, targetID string) error {
+// Block blocks an account. A non-empty gameID marks an in-game block, so a disguised-robot
+// opponent is recorded as a per-game block; it is empty for a settings-screen block.
+func (c *Client) Block(ctx context.Context, userID, targetID, gameID string) error {
 	return c.do(ctx, http.MethodPost, "/api/v1/user/blocks", userID, "",
-		map[string]string{"account_id": targetID}, nil)
+		map[string]string{"account_id": targetID, "game_id": gameID}, nil)
 }
 
 // Unblock removes a block.