fix(authz): scope import, approvals, activity, and heartbeat routes (#3315)

## Thinking Path

> - Paperclip orchestrates AI agents and company-scoped control-plane
actions for zero-human companies.
> - This change touches the server authz boundary around company
portability, approvals, activity, and heartbeat-run operations.
> - The vulnerability was that board-authenticated callers could cross
company boundaries or create new companies through import paths without
the same authorization checks enforced elsewhere.
> - Once that gap existed, an attacker could chain it into higher-impact
behavior through agent execution paths.
> - The fix needed to harden every confirmed authorization gap in the
reported chain, not just the first route that exposed it.
> - This pull request adds the missing instance-admin and company-access
checks and adds regression tests for each affected route.
> - The benefit is that cross-company actions and new-company import
flows now follow the same control-plane authorization rules as the rest
of the product.

## What Changed

- Required instance-admin access for `new_company` import preview/apply
flows in `server/src/routes/companies.ts`.
- Required company access before approval decision routes in
`server/src/routes/approvals.ts`.
- Required company access for activity creation and heartbeat-run issue
listing in `server/src/routes/activity.ts`.
- Required company access before heartbeat cancellation in
`server/src/routes/agents.ts`.
- Added regression coverage in the corresponding server route tests.

## Verification

- `pnpm --filter @paperclipai/server exec vitest run
src/__tests__/company-portability-routes.test.ts
src/__tests__/approval-routes-idempotency.test.ts
src/__tests__/activity-routes.test.ts
src/__tests__/agent-permissions-routes.test.ts`
- `pnpm --filter @paperclipai/server typecheck`
- Prior verification on the original security patch branch also included
`pnpm build`.

## Risks

- Low code risk: the change is narrow and only adds missing
authorization gates to existing routes.
- Operational risk: the advisory is already public, so this PR should be
merged quickly to minimize the public unpatched window.
- Residual product risk remains around open signup / bootstrap defaults,
which was intentionally left out of this patch because the current
first-user onboarding flow depends on it.

## Model Used

- OpenAI GPT-5 Codex coding agent with tool use and local code execution
in the Codex CLI environment.

## Checklist

- [x] I have included a thinking path that traces from project context
to this change
- [x] I have specified the model used (with version and capability
details)
- [x] I have run tests locally and they pass
- [x] I have added or updated tests where applicable
- [ ] If this change affects the UI, I have included before/after
screenshots
- [ ] I have updated relevant documentation to reflect my changes
- [x] I have considered and documented any risks above
- [x] I will address all Greptile and reviewer comments before
requesting merge

Co-authored-by: Forgotten <forgottenrunes@protonmail.com>

server/src/routes/approvals.ts

@@ -1,4 +1,4 @@
-import { Router } from "express";
+import { Router, type Request } from "express";
 import type { Db } from "@paperclipai/db";
 import {
   addApprovalCommentSchema,
@@ -34,6 +34,15 @@ export function approvalRoutes(db: Db) {
   const secretsSvc = secretService(db);
   const strictSecretsMode = process.env.PAPERCLIP_SECRETS_STRICT_MODE === "true";
 
+  async function requireApprovalAccess(req: Request, id: string) {
+    const approval = await svc.getById(id);
+    if (!approval) {
+      return null;
+    }
+    assertCompanyAccess(req, approval.companyId);
+    return approval;
+  }
+
   router.get("/companies/:companyId/approvals", async (req, res) => {
     const companyId = req.params.companyId as string;
     assertCompanyAccess(req, companyId);
@@ -121,6 +130,10 @@ export function approvalRoutes(db: Db) {
   router.post("/approvals/:id/approve", validate(resolveApprovalSchema), async (req, res) => {
     assertBoard(req);
     const id = req.params.id as string;
+    if (!(await requireApprovalAccess(req, id))) {
+      res.status(404).json({ error: "Approval not found" });
+      return;
+    }
     const { approval, applied } = await svc.approve(
       id,
       req.body.decidedByUserId ?? "board",
@@ -216,6 +229,10 @@ export function approvalRoutes(db: Db) {
   router.post("/approvals/:id/reject", validate(resolveApprovalSchema), async (req, res) => {
     assertBoard(req);
     const id = req.params.id as string;
+    if (!(await requireApprovalAccess(req, id))) {
+      res.status(404).json({ error: "Approval not found" });
+      return;
+    }
     const { approval, applied } = await svc.reject(
       id,
       req.body.decidedByUserId ?? "board",
@@ -243,6 +260,10 @@ export function approvalRoutes(db: Db) {
     async (req, res) => {
       assertBoard(req);
       const id = req.params.id as string;
+      if (!(await requireApprovalAccess(req, id))) {
+        res.status(404).json({ error: "Approval not found" });
+        return;
+      }
       const approval = await svc.requestRevision(
         id,
         req.body.decidedByUserId ?? "board",