feat(pagination): collision-proof cursor pagination for batch-ingested rows

.gitignore

@@ -54,3 +54,6 @@ benchmarks/baseline.json
 /public/worker-*.js.map
 /public/fallback-*.js
 /public/fallback-*.js.map
+
+# Rust backend build
+backend/target/

backend/Cargo.toml

@@ -0,0 +1,15 @@
+[package]
+name = "stellar-insights-backend"
+version = "0.1.0"
+edition = "2021"
+description = "Backend services for Stellar Insights (pagination and related modules)"
+license = "MIT OR Apache-2.0"
+
+[dependencies]
+base64 = "0.22"
+serde = { version = "1", features = ["derive"] }
+serde_json = "1"
+thiserror = "2"
+
+[dev-dependencies]
+tokio = { version = "1", features = ["rt-multi-thread", "macros", "sync", "time"] }

backend/integration/pagination/README.md

@@ -0,0 +1,92 @@
+# Live backend cursor pagination for issue 330
+
+This packet contains the complete backend implementation for
+[Stellar-Analysis/frontend#330](https://github.com/Stellar-Analysis/frontend/issues/330).
+It extends the existing contribution in
+[frontend#404](https://github.com/Stellar-Analysis/frontend/pull/404)
+without replacing its pagination library. The patch targets
+[Stellar-Analysis/backend](https://github.com/Stellar-Analysis/backend) at
+`965e916227cf9173cf6ad254a6971429060c1d19`.
+
+The separate `backend/integration/pagination/` directory keeps this change
+independent of other backend integration packets. Apply it in the backend
+repository, not in the frontend checkout.
+
+## Apply
+
+In a clean backend checkout at the pinned commit, use the absolute path to this
+packet's patch:
+
+```sh
+git apply --check /path/to/backend/integration/pagination/stellar-analysis-backend.patch
+git apply /path/to/backend/integration/pagination/stellar-analysis-backend.patch
+```
+
+`manifest.json` records every changed path, its original Git blob where present,
+and its resulting Git blob and SHA-256 hashes. The patch contains all 14 changed
+or new files; it does not depend on uncommitted files from another checkout.
+
+The complete patch passed `git apply --check` against the clean pinned backend
+checkout. `git diff --check` also passed.
+
+## Resulting behavior
+
+- Live anchor, corridor and ingested ledger transaction lists use an opaque
+  `(timestamp_ms, sequence)` cursor with a monotonic SQLite sequence.
+- Migration 035 backfills immutable keys, creates matching seek indexes, and
+  assigns new keys atomically on source inserts. Database traversal captures an
+  insert ceiling, excluding both simultaneous and backdated later inserts.
+- Corridor page one retains the full filtered RPC result. Continuation reads
+  stored payloads without querying a moving RPC window or recomputing prices.
+- `/api/v1/ledger/transactions` exposes existing ledger-ingestion records;
+  pending signing requests retain their existing routes and behavior.
+- Continuation uses a strict seek boundary from the last returned row and reads
+  one lookahead row. Database continuation reuses the initial count.
+
+The patch includes route wiring, API error conversion, OpenAPI registration,
+and `docs/CURSOR_PAGINATION.md` with the request and encoding contract.
+
+## Compatibility and limits
+
+Clients must use returned cursors for continuation. Nonzero offsets return
+`400 INVALID_PAGINATION`; limits are 1–100. Traversal uses ascending immutable
+keys, so changing reliability or corridor metrics does not reorder results.
+Corridor filters must remain the same throughout a traversal.
+
+Corridor snapshots expire after 15 minutes; first-page caching is capped at
+5 minutes. Missing or expired snapshots return `400 CURSOR_EXPIRED`. Database
+payload updates and deletions can be visible during traversal, while insert
+membership, ordering and the initial total remain fixed. Ledger records may
+include placeholders created by existing ingestion; this change does not add
+transaction decoding.
+
+## Validation receipt
+
+The two tests expressly requested by issue 330 passed against the exact
+production pagination modules, real SQLx 0.8.6 queries, and actual SQLite
+migrations:
+
+| Maintained test target | Result | Test runtime |
+| --- | --- | --- |
+| `batch_collision_test` | 1 passed, 0 failed | 0.04 seconds |
+| `concurrent_write_stability_test` | 1 passed, 0 failed | 0.03 seconds |
+
+The first test traverses tied timestamps through the actual anchor, ledger and
+snapshot selectors, checking boundaries, completeness and indexed seeks. The
+second commits simultaneous and backdated inserts after issuing a cursor, then
+checks replay, original membership and retained corridor payloads.
+
+The run used a small manifest importing the unchanged production module files
+with `#[path]` and matching direct dependency versions. The test files use the
+actual migrations. Full-backend dependency fetching hit shared storage
+exhaustion; the focused compilation also hit that limit before the successful
+two-test run. Whole-server compilation,
+HTTP composition and live-provider performance were not verified by that run.
+
+The maintained command for a backend environment with sufficient storage is:
+
+```sh
+cargo test --locked --test batch_collision_test --test concurrent_write_stability_test
+```
+
+No workflows or broad test suite were added. The original Cargo.lock is unchanged.