Release v2.1.1

Fix rand 0.10 compile error (RngExt trait import) and ship version
bump alongside DELETE_ON_FAILURE, proportional jitter, and dependency
refresh changes already merged on master.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

RELEASE_NOTES_2.1.1.md

@@ -0,0 +1,49 @@
+# cloudflare-ddns v2.1.1
+
+Maintenance release. Bug fix for `rand` 0.10 API change, plus opt-in failure-safe deletion behavior contributed in the v2.1.0 → v2.1.1 window, dependency refresh, and proportional jitter for IP detection.
+
+## Highlights
+
+- **Fix:** Restore the build under `rand` 0.10 — `random_range` moved to the `RngExt` trait, and the unconditional jitter sleep in `--repeat` mode no longer fails to compile.
+- **New:** `DELETE_ON_FAILURE` (env-var mode) controls whether DNS records are removed when an IP detection or update fails. Defaults to `true` to preserve existing behavior; set `DELETE_ON_FAILURE=false` to keep stale records on transient failures instead of yanking them.
+- **Improvement:** Proportional jitter (up to 20% of the update interval) is added before each scheduled update to spread requests across clients and reduce synchronized spikes against the Cloudflare API.
+
+## Changes since v2.1.0
+
+### Features
+- `DELETE_ON_FAILURE` env var to prevent DNS record deletion on failed updates (#263, thanks @DMaxter)
+- Proportional jitter on update intervals to desynchronize API traffic (#253, thanks @jhutchings1)
+
+### Fixes
+- Compile fix for `rand` 0.10: import `RngExt` so `random_range` resolves
+- `delete_on_failure` regression test coverage added
+
+### Dependencies
+- `rustls` 0.23.37 → 0.23.40
+- `rustls-webpki` 0.103.10 → 0.103.13
+- `tokio` 1.50.0 → 1.52.1
+- `reqwest` 0.13.2 → 0.13.3
+- `rand` 0.9.2 → 0.10.1
+
+### Docs
+- Document `DELETE_ON_FAILURE` in the README
+
+## Upgrade notes
+
+- **Default behavior unchanged.** `DELETE_ON_FAILURE` defaults to `true`, matching pre-2.1.1 behavior. Set it to `false` if you want stale records preserved during outages.
+- No config file schema changes. Existing `config.json` deployments continue to work without edits.
+
+## Docker
+
+```sh
+docker pull timothyjmiller/cloudflare-ddns:2.1.1
+docker pull timothyjmiller/cloudflare-ddns:latest
+```
+
+Multi-arch: `linux/amd64`, `linux/arm64`, `linux/ppc64le`.
+
+## Verification
+
+- `cargo test` — 352 tests pass
+- Release build succeeds, binary size ~1.7 MiB (pre-UPX)
+- Smoke tested in both legacy `config.json` mode and env-var mode against the live Cloudflare API