Add publish API with modular service layer

Add tRPC publish endpoint, project version parsing, config CRUD, and
client services for Modrinth/CurseForge integration.

src/app/api/publish/[trpc]/route.ts

@@ -0,0 +1,12 @@
+import { fetchRequestHandler } from "@trpc/server/adapters/fetch";
+import { appRouter } from "@/services/publish";
+
+const handler = (req: Request) =>
+  fetchRequestHandler({
+    endpoint: "/api/publish",
+    req,
+    router: appRouter,
+    createContext: () => ({}),
+  });
+
+export { handler as GET, handler as POST };