fix(#1346): paginate the ownership-chain history endpoint

[jarik2014]

Closes #1346.

The gap

contract/src/module/ownership_chain/pagination.rs existed with a working paginate() but was never reachable: mod.rs did not declare the module, so nothing compiled it, and no handler called it. That is the whole issue — not a missing algorithm, a missing wire.

What this does

• Declares the pagination module in src/module/ownership_chain/mod.rs.
• Connects cursor / page_size to the endpoint that actually serves the chain: GET /verify/:hash/history, which the router in src/lib.rs mounts and which already returns the ownership-chain records.
• Opt-in, so nothing breaks: with no query params the response is unchanged (whole chain, next_cursor: null). Pass page_size and/or cursor and you get a page plus next_cursor; count stays the total length of the chain.
• Adds next_cursor to HistoryResponse (additive field).
• Tests: 7 unit tests on paginate() (first/last page, exact fit, cursor at and past the end, zero page size, empty input) and 5 integration tests on the mounted endpoint (full chain without params, first page reports the cursor, last page has none, cursor past the end is a 200 with an empty page rather than a 500, and page_size is capped).

One thing worth knowing

get_transfer_history in src/lib.rs is not mounted by the live router — routes.rs declares GET /transfer/:document_hash, but the app the tests build (app() in lib.rs) never adds it, so that handler is unreachable and paginating it would have changed nothing. I first wired the pagination there, found the route missing, and moved it to /verify/:hash/history. Both handlers exist; only one is served. If you want the /transfer/:document_hash route mounted as well, say so and I will add it in a separate change.

Pre-existing breakage this branch has to carry

contract/ does not compile on main at all, so no test could run:

error[E0277]: the trait bound `DateTime<Utc>: serde::Deserialize<'de>` is not satisfied   --> src/event.rs:17:20
error[E0277]: the trait bound `RateLimiter<...>: Clone` is not satisfied                  --> src/lib.rs:77:5
error[E0382]: borrow of moved value: `data_key`                                           --> src/stellar.rs:788:9
error: could not compile `stellar-doc-verifier` (lib) due to 5 previous errors
error: could not compile `stellar-doc-verifier` (lib test) due to 6 previous errors

The first commit fixes exactly those (chrono serde feature, the rate limiter behind an Arc, the moved data_key in the mock), plus one more that only shows up once the tests compile: the integration test target imports tower::util::ServiceExt, which needs tower's util feature enabled in Cargo.toml. Split it out if you prefer to land the unbreak on its own — it is one commit and nothing in it is specific to pagination.

Verification (stable toolchain; contract/rust-toolchain.toml pins 1.82, which cannot even parse a lockfile dependency requiring edition2024)

$ cargo test --lib pagination
test result: ok. 7 passed; 0 failed; 0 ignored

$ cargo test --test handler_integration_tests
test test_verify_history_without_params_returns_the_whole_chain ... ok
test test_verify_history_first_page_reports_next_cursor ... ok
test test_verify_history_last_page_has_null_next_cursor ... ok
test test_verify_history_cursor_past_the_end_is_empty_not_500 ... ok
test test_verify_history_page_size_is_capped_at_the_maximum ... ok
test result: ok. 19 passed; 0 failed; 0 ignored

$ cargo test --all
test result: FAILED. 142 passed; 11 failed   (lib)

The 11 remaining failures are pre-existing harness problems in code this change does not touch — hash_validator::tests::sha256/sha512_rejects_non_ascii_unicode_and_binary_characters, six stellar::tests::* (mock keypanics with Invalid secret key: InvalidStrKeyChecksum, Horizon 404/500 mocks), and two webhook::tests::*. They cannot be compared against main directly because main does not compile; the comparison is against the unbreak commit alone, which I will paste here when that run finishes.

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[jarik2014]

Baseline comparison, as promised — this is the "not mine" arm.

Unbreak commit alone, with the pagination wiring reverted (git revert cd5a7df), same toolchain, same target dir:

running 146 tests
test result: FAILED. 135 passed; 11 failed

This branch:

running 153 tests
test result: FAILED. 142 passed; 11 failed

The seven extra tests are the new pagination::tests, all passing, and the failing names are identical in both arms: 2 × hash_validator::tests::*_rejects_non_ascii_unicode_and_binary_characters, 6 × stellar::tests::* (Invalid secret key: InvalidStrKeyChecksum in the mock, plus the Horizon 404/500 mocks) and 2 × webhook::tests::*. Nothing in this diff touches those modules — they are broken on the unbreak-only tree already, and they need a real keypair/test fixture to fix, which is separate work.