feat: add post3 s3 proxy for postgresql

Signed-off-by: kjuulh <contact@kjuulh.io>

todos/POST3-011-examples.md

@@ -0,0 +1,29 @@
+# POST3-011: Usage examples
+
+**Status:** Done
+**Priority:** P1
+**Blocked by:** POST3-008
+
+## Description
+
+Create runnable examples demonstrating how to use post3 with both the SDK and shell tools.
+
+## What was built
+
+### Rust examples (`crates/post3-sdk/examples/`)
+- [x] `basic.rs` — create bucket, put/get/delete object, list objects with prefix filter
+- [x] `metadata.rs` — put object with custom metadata (x-amz-meta-*), retrieve via head/get
+- [x] `aws_sdk_direct.rs` — use aws-sdk-s3 directly (without post3-sdk wrapper), shows raw config
+
+### Script examples (`examples/`)
+- [x] `aws-cli.sh` — shell script demonstrating all operations via `aws` CLI
+- [x] `curl.sh` — shell script demonstrating raw HTTP calls with curl
+
+### mise tasks
+- [x] `example:basic` — runs the basic Rust example
+- [x] `example:metadata` — runs the metadata Rust example
+- [x] `example:aws-sdk` — runs the raw aws-sdk-s3 example
+- [x] `example:cli` — runs the AWS CLI example script
+- [x] `example:curl` — runs the curl example script
+
+All examples tested and verified working against live server.