Add multiple terminals per task and saved commands that start one

internal/store/migrations/087-add-saved-commands.sql

@@ -0,0 +1,7 @@
+CREATE TABLE saved_commands (
+	id TEXT PRIMARY KEY,
+	owner TEXT NOT NULL REFERENCES users(login),
+	name TEXT NOT NULL,
+	command TEXT NOT NULL
+);
+CREATE INDEX saved_commands_owner ON saved_commands(owner, name);