doc: add release history for release v0.3.0 (#743)

Co-authored-by: Gang Wu <ustcwg@gmail.com>

Author: zhjwpku

mkdocs/docs/releases.md

@@ -21,11 +21,27 @@
 
 | Version | Date | Links |
 |---------|------|-------|
+| 0.3.0 | June 14, 2026 | [Release Notes](https://github.com/apache/iceberg-cpp/releases/tag/v0.3.0) · [Source](https://dist.apache.org/repos/dist/release/iceberg/apache-iceberg-cpp-0.3.0/) · [Blog Post](https://iceberg.apache.org/blog/apache-iceberg-cpp-0.3.0-release/) |
 | 0.2.0 | January 26, 2026 | [Release Notes](https://github.com/apache/iceberg-cpp/releases/tag/v0.2.0) · [Source](https://dist.apache.org/repos/dist/release/iceberg/apache-iceberg-cpp-0.2.0/) · [Blog Post](https://iceberg.apache.org/blog/apache-iceberg-cpp-0.2.0-release/) |
 | 0.1.0 | September 10, 2025 | [Release Notes](https://github.com/apache/iceberg-cpp/releases/tag/v0.1.0) · [Source](https://archive.apache.org/dist/iceberg/apache-iceberg-cpp-0.1.0/) |
 
 For the full changelog of each release, see the [GitHub Releases page](https://github.com/apache/iceberg-cpp/releases).
 
+## 0.3.0
+
+- Extend table scan planning with v2 delete support, manifest filtering, and projection
+- Incremental scan planning with append-only and basic changelog scan support
+- REST catalog improvements including initial OAuth2 support with auto-refresh, basic authentication, snapshot loading mode, namespace separators, and server-side scan planning
+- New table metadata update including partition statistics, schema update, and expire snapshots with file cleanup support
+- Transaction with retry, and scaffolding work on MergingSnapshotUpdate for update, delete, overwrite, etc.
+- SQL catalog support backed by SQLite, PostgreSQL, and MySQL stores
+- File scan task reader with v2 deletes support
+- V2 data writer support and writer metrics collection
+- Groundwork for scan and commit metrics reporting
+- Puffin metadata and reader/writer support
+- Initial v3 support with the unknown and nanosecond timestamp types
+- FileIO enrichment including new InputFile and OutputFile interfaces, bulk delete and S3 integration
+
 ## 0.2.0
 
 - Table scan planning with V2 delete and filtering support