feat(TC-500): integrate native sharing into TinyChat release

[samgbafa]

TC-500 production-lineage integration

Ports the reviewed native-sharing architecture from main PR #229 onto the exact TinyChat production candidate base 461e387b74c6760c5b48a265dca6a258667837c0 (binary version remains 1.17.0 in this integration PR).

Scope and preservation

• Preserves TinyChat meeting-publication, legacy-freeze, quota, and route behavior from the production candidate.
• Retains the production digest-pinned deployment workflow; adds only the Policy/v3 delivery-authorization probe.
• Keeps /policy/v3 admission/control only and generic /delegate + /invoke as the data plane; no Share-specific data-plane route.
• Ports Policy/v3 authenticated status/freshness, expiry liveness, generic revocation, exact-body replay, encrypted recipient delivery, trust-bundle contract, and Rust 1.97.1 pinning.

Verification

• cargo fmt --all -- --check
• RUSTFLAGS='-Dwarnings' cargo check -p tinycloud-node --tests
• RUSTFLAGS='-Dwarnings' cargo clippy -p tinycloud-node --all-targets -- -D warnings
• cargo test -p tinycloud-node policy_v3 --lib -- --test-threads=1 (26 passed)
• cargo test -p tinycloud-node legacy_freeze --lib -- --test-threads=1 (5 passed)
• cargo test -p tinycloud-node production_route_tests --lib (1 passed)
• cargo test -p tinycloud-node publication_route --lib (5 passed)
• cargo test -p tinycloud-node --lib -- --test-threads=1 (363 passed)
• cargo test -p tinycloud-core publication --lib -- --test-threads=1 (21 passed)
• cargo test -p tinycloud-core legacy_freeze --lib -- --test-threads=1 (11 passed)
• node scripts/check-deployment-policy-probes.mjs
• cargo test --workspace -- --test-threads=1

Release recommendation

Do not branch-deploy this integration or alter the current 1.17.0 candidate. Following independent security/TinyChat review and merge, prepare a separately versioned 1.17.1 release from this release branch, then use the existing digest-pinned release workflow.

Please obtain independent security and TinyChat regression review before merge.

Refs TC-500.