feat(httpclient)!: promote to v1.0.0 — retry-on-429 with Retry-After, DoJSONRequest, bump deps

Extend retry loop to handle HTTP 429 Too Many Requests: when the server includes a
Retry-After header, that duration is used as the retry delay; otherwise falls back to
the configured BackOffDelay. Add DoJSONRequest[Req, Resp] free function that serialises
the request body as JSON, sets Content-Type, and delegates response decoding to DoJSON.
Bump logz and xerrors from v0.9.0 to v1.0.0. API committed as stable.

CHANGELOG.md

@@ -5,6 +5,24 @@ All notable changes to this module will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this module adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [1.0.0] — 2026-05-12
+
+### Added
+
+- `DoJSONRequest[Req, Resp any](ctx, client, method, rawURL, body) (*Resp, error)` — free generic function that serialises `body` as JSON, constructs the `*http.Request` with `Content-Type: application/json`, and delegates response decoding to `DoJSON`. Complements `DoJSON` for POST/PUT/PATCH calls; use `DoJSON` for GET/DELETE where there is no request body.
+
+### Changed
+
+- Retry loop now handles HTTP 429 Too Many Requests: a 429 response triggers a retry (previously only `>= 500` did). When the server includes a `Retry-After` header with an integer seconds value, that duration is used as the retry delay for that attempt; otherwise the configured `BackOffDelay` applies.
+- `logz` and `xerrors` dependencies bumped from v0.9.0 to v1.0.0.
+
+### Unchanged
+
+All other API (`Client`, `Config`, `DefaultConfig`, `New`, `NewWithDefaults`, `DoJSON`,
+`MapStatusToError`) is API-compatible with v0.9.0.
+
+[1.0.0]: https://code.nochebuena.dev/go/httpclient/releases/tag/v1.0.0
+
 ## [0.9.0] - 2026-03-18
 
 ### Added