Add end-to-end HTTP tests under backend/test/e2e/ using Node.js built-in
test runner (node:test) and native fetch. Tests run through the devenv
nginx proxy on port 3450.
Test suites (19 tests total):
- auth-flow: demo profile creation, login, session cookies, access tokens
- export-binfile: file creation, export to asset URL via SSE
- asset-download: download with cookie/token auth, 401 without auth,
S3 redirect behavior, full export-to-download flow
Key findings documented in tests:
- nginx @handle_redirect intercepts backend 307 and proxies to S3 directly,
stripping the client Authorization header (bug does not reproduce in devenv)
- SSE end event uses ~#uri tagged format for URLs
- Unauthenticated RPC returns uuid/zero profile (not null)
AI-assisted-by: mimo-v2.5-pro
Signed-off-by: Andrey Antukh <niwi@niwi.nz>
