[Herklos]

Updates four stale tests in examples/app/backend/tests/test_edge.py so they match how the server handles author proofs, the withKeyring optimization, and rendezvous TTL expiry.

• Reject spoofed authorPubkey with 403 and assert no document is stored
• Rename and rewrite the author proof test: incomplete proof returns 400, invalid proof returns 403
• Expect no keyring field when the reader cap scope does not cover _keyring
• Use document-level ts in the TTL fixture so expired rendezvous reads return empty data

Tests only; no production code changes. Full backend suite: 121 passed.