feat: add model_groups table and default seed data

internal/db/db.go

@@ -122,6 +122,16 @@ func (db *DB) RunMigrations() error {
             created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
             last_used_at DATETIME,
             FOREIGN KEY (client_id) REFERENCES clients(client_id) ON DELETE CASCADE
+        )`,
+		`CREATE TABLE IF NOT EXISTS model_groups (
+            id TEXT PRIMARY KEY,
+            strategy TEXT NOT NULL DEFAULT 'heuristic',
+            selector_model TEXT,
+            targets TEXT NOT NULL DEFAULT '[]',
+            complexity_threshold INTEGER,
+            heuristic_rules TEXT,
+            created_at DATETIME DEFAULT CURRENT_TIMESTAMP,
+            updated_at DATETIME DEFAULT CURRENT_TIMESTAMP
         )`,
 	}
 
@@ -177,6 +187,19 @@ func (db *DB) RunMigrations() error {
 		return fmt.Errorf("failed to insert default client: %w", err)
 	}
 
+	// Seed default model groups
+	defaultGroups := []struct {
+		id, strategy, targets string
+	}{
+		{"deepseek-auto", "heuristic", `["deepseek-chat","deepseek-reasoner"]`},
+		{"openai-auto", "heuristic", `["gpt-4o-mini","gpt-4o"]`},
+		{"gemini-auto", "heuristic", `["gemini-2.0-flash","gemini-2.5-pro"]`},
+	}
+	for _, g := range defaultGroups {
+		db.Exec(`INSERT OR IGNORE INTO model_groups (id, strategy, targets) VALUES (?, ?, ?)`,
+			g.id, g.strategy, g.targets)
+	}
+
 	return nil
 }
 
@@ -262,3 +285,14 @@ type ClientToken struct {
 	CreatedAt time.Time  `db:"created_at"`
 	LastUsedAt *time.Time `db:"last_used_at"`
 }
+
+type ModelGroup struct {
+	ID                  string    `db:"id" json:"id"`
+	Strategy            string    `db:"strategy" json:"strategy"`
+	SelectorModel       *string   `db:"selector_model" json:"selector_model"`
+	Targets             string    `db:"targets" json:"targets"` // JSON array
+	ComplexityThreshold *int      `db:"complexity_threshold" json:"complexity_threshold"`
+	HeuristicRules      *string   `db:"heuristic_rules" json:"heuristic_rules"`
+	CreatedAt           time.Time `db:"created_at" json:"created_at"`
+	UpdatedAt           time.Time `db:"updated_at" json:"updated_at"`
+}