refactoring the api endpoints to be separate files to reduce context usage

apps/server/src/routes/git/index.ts

@@ -0,0 +1,16 @@
+/**
+ * Git routes - HTTP API for git operations (non-worktree)
+ */
+
+import { Router } from "express";
+import { createDiffsHandler } from "./routes/diffs.js";
+import { createFileDiffHandler } from "./routes/file-diff.js";
+
+export function createGitRoutes(): Router {
+  const router = Router();
+
+  router.post("/diffs", createDiffsHandler());
+  router.post("/file-diff", createFileDiffHandler());
+
+  return router;
+}