Refactor backend database connection, migration, seed

backend/migrations/20251017065315_00002_create_settings_table.sql

@@ -0,0 +1,14 @@
+-- +goose Up
+-- +goose StatementBegin
+CREATE TABLE IF NOT EXISTS settings (
+    key   TEXT PRIMARY KEY,
+    value TEXT NOT NULL
+);
+INSERT INTO settings (key, value) VALUES ('finalize_time', '10:30');
+INSERT INTO settings (key, value) VALUES ('seeded', 'false');
+-- +goose StatementEnd
+
+-- +goose Down
+-- +goose StatementBegin
+DROP TABLE IF EXISTS settings;
+-- +goose StatementEnd