Add server routes for companies, approvals, costs, and dashboard

New routes: companies, approvals, costs, dashboard, authz. New
services: companies, approvals, costs, dashboard, heartbeat,
activity-log. Add auth middleware and structured error handling.
Expand existing agent and issue routes with richer CRUD operations.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

server/src/errors.ts

@@ -0,0 +1,34 @@
+export class HttpError extends Error {
+  status: number;
+  details?: unknown;
+
+  constructor(status: number, message: string, details?: unknown) {
+    super(message);
+    this.status = status;
+    this.details = details;
+  }
+}
+
+export function badRequest(message: string, details?: unknown) {
+  return new HttpError(400, message, details);
+}
+
+export function unauthorized(message = "Unauthorized") {
+  return new HttpError(401, message);
+}
+
+export function forbidden(message = "Forbidden") {
+  return new HttpError(403, message);
+}
+
+export function notFound(message = "Not found") {
+  return new HttpError(404, message);
+}
+
+export function conflict(message: string, details?: unknown) {
+  return new HttpError(409, message, details);
+}
+
+export function unprocessable(message: string, details?: unknown) {
+  return new HttpError(422, message, details);
+}