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/__tests__/company-portability-routes.test.ts

@@ -175,4 +175,50 @@ describe("company portability routes", () => {
     expect(res.status).toBe(403);
     expect(res.body.error).toContain("Board access required");
   });
+
+  it("requires instance admin for new-company import preview", async () => {
+    const app = await createApp({
+      type: "board",
+      userId: "user-1",
+      companyIds: ["11111111-1111-4111-8111-111111111111"],
+      source: "session",
+      isInstanceAdmin: false,
+    });
+
+    const res = await request(app)
+      .post("/api/companies/import/preview")
+      .send({
+        source: { type: "inline", files: { "COMPANY.md": "---\nname: Test\n---\n" } },
+        include: { company: true, agents: true, projects: false, issues: false },
+        target: { mode: "new_company", newCompanyName: "Imported Test" },
+        collisionStrategy: "rename",
+      });
+
+    expect(res.status).toBe(403);
+    expect(res.body.error).toContain("Instance admin");
+    expect(mockCompanyPortabilityService.previewImport).not.toHaveBeenCalled();
+  });
+
+  it("requires instance admin for new-company import apply", async () => {
+    const app = await createApp({
+      type: "board",
+      userId: "user-1",
+      companyIds: ["11111111-1111-4111-8111-111111111111"],
+      source: "session",
+      isInstanceAdmin: false,
+    });
+
+    const res = await request(app)
+      .post("/api/companies/import")
+      .send({
+        source: { type: "inline", files: { "COMPANY.md": "---\nname: Test\n---\n" } },
+        include: { company: true, agents: true, projects: false, issues: false },
+        target: { mode: "new_company", newCompanyName: "Imported Test" },
+        collisionStrategy: "rename",
+      });
+
+    expect(res.status).toBe(403);
+    expect(res.body.error).toContain("Instance admin");
+    expect(mockCompanyPortabilityService.importBundle).not.toHaveBeenCalled();
+  });
 });