[backend] Fix linter errors (whoops)

backend/drizzle.config.ts

···
 import { Config } from "./src/config.ts";
 
 const config = Config.getInstance().getConfig();
-let dbname;
-
-dbname = config.database.name;
+const dbname = config.database.name;
 
 export default defineConfig({
 	out: "./drizzle",

backend/src/config.ts

···
 	network: {
 		firehose: string | "jetstream1.us-east.bsky.network";
 		serviceDid: string | "did:web:localhost%3A9090";
-		didSigningKey: string | "did:key:zDnaeuuRRQuYp4S76LwosLhHbpU1HJcg6S5oJAUHmdZLVdLM5";
+		didSigningKey:
+			| string
+			| "did:key:zDnaeuuRRQuYp4S76LwosLhHbpU1HJcg6S5oJAUHmdZLVdLM5";
 	};
 }
 

backend/src/routes/well-known.ts

···
 
 const serviceDid: string = config.network.serviceDid;
 const signingKey: string = config.network.didSigningKey;
-let baseUrl: string = config.baseUrl
+let baseUrl: string = config.baseUrl;
 
 if (!baseUrl.startsWith("http://") || !baseUrl.startsWith("https://")) {
 	baseUrl = `http://${baseUrl.replace(/^https?:\/\//, "")}`;