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/middleware/error-handler.ts

@@ -1,6 +1,7 @@
 import type { Request, Response, NextFunction } from "express";
 import { ZodError } from "zod";
 import { logger } from "./logger.js";
+import { HttpError } from "../errors.js";
 
 export function errorHandler(
   err: unknown,
@@ -8,6 +9,14 @@ export function errorHandler(
   res: Response,
   _next: NextFunction,
 ) {
+  if (err instanceof HttpError) {
+    res.status(err.status).json({
+      error: err.message,
+      ...(err.details ? { details: err.details } : {}),
+    });
+    return;
+  }
+
   if (err instanceof ZodError) {
     res.status(400).json({ error: "Validation error", details: err.errors });
     return;