feat(mini): add -bucket flag to pre-create an S3 bucket on startup (#9302)

* feat(mini): add -bucket flag to pre-create an S3 bucket on startup

Lets users hand a pre-provisioned object store to clients/CI without a
post-start `weed shell s3.bucket.create` step. The flag is a no-op when
empty (default) and idempotent on subsequent starts.

* mini: bound bucket-creation RPCs with a timeout off miniClientsCtx

Address PR review feedback: derive the lookup/mkdir context from
miniClientsCtx() so Ctrl+C cancels the bucket RPCs, and cap with a 5s
timeout so a stalled filer cannot block the welcome message
indefinitely. Also wrap the DoMkdir error for parity with the lookup
path.

* mini: fall back to S3_BUCKET env var for -bucket

Mirrors the existing -s3.externalUrl / S3_EXTERNAL_URL pattern so
container/Kubernetes deployments can pre-create the bucket via env
without overriding the entrypoint command.

* docs(readme): lead weed mini quick start with credentials + bucket

Promote the one-line setup (env vars + bucket) so users get a
ready-to-use S3 endpoint without hopping between sections to find
credential and bucket setup.

* mini: accept comma-separated -bucket list

Lets a single startup pre-create multiple S3 buckets, e.g.
-bucket=bucket1,bucket2 (or S3_BUCKET=bucket1,bucket2). Names are
trimmed and deduped; per-bucket errors are logged and the loop continues
so one bad name does not block the rest.

* mini: add -tableBucket flag for pre-creating S3 Tables buckets

Mirrors -bucket but creates S3 Tables (Iceberg) buckets via
s3tables.Manager so users can hand the all-in-one binary a ready-to-use
table catalog without a follow-up weed shell call. Comma-separated, env
fallback to S3_TABLE_BUCKET, idempotent on restart, owned by the
DefaultAccountID placeholder.

* mini: use errors.Is for ErrNotFound check in bucket lookup

Matches the rest of the codebase (~20 call sites in weed/s3api). The
direct equality works today because LookupEntry returns ErrNotFound
unwrapped, but errors.Is future-proofs against any future wrapping.

README.md

@@ -80,28 +80,29 @@ Table of Contents
 
 
 ## Quick Start with weed mini ##
-The easiest way to get started with SeaweedFS for development and testing:
 
-* Download the latest binary from https://github.com/seaweedfs/seaweedfs/releases and unzip a single binary file `weed` or `weed.exe`.
-
-Example:
+Download the latest binary from https://github.com/seaweedfs/seaweedfs/releases and unzip the single `weed` (or `weed.exe`) file. Then start a ready-to-use S3 object store with credentials and a pre-created bucket in one command:
 
 ```bash
-# remove quarantine on macOS
-# xattr -d com.apple.quarantine  ./weed
-
+AWS_ACCESS_KEY_ID=admin \
+AWS_SECRET_ACCESS_KEY=secret \
+S3_BUCKET=my-bucket \
 ./weed mini -dir=/data
 ```
 
-This single command starts a complete SeaweedFS setup with:
+That's it — the S3 endpoint is at http://localhost:8333, `my-bucket` already exists, and `admin`/`secret` are valid credentials. `S3_BUCKET` accepts a comma-separated list (e.g. `raw,processed`); use `S3_TABLE_BUCKET` for S3 Tables (Iceberg) buckets. Drop any of the env vars to skip that piece (no AWS keys → S3 runs in unauthenticated "Allow All" mode for development).
+
+The same command starts everything else too:
+- **S3 Endpoint**: http://localhost:8333
 - **Master UI**: http://localhost:9333
 - **Volume Server**: http://localhost:9340
 - **Filer UI**: http://localhost:8888
-- **S3 Endpoint**: http://localhost:8333
 - **WebDAV**: http://localhost:7333
 - **Admin UI**: http://localhost:23646
 
-Perfect for development, testing, learning SeaweedFS, and single node deployments!
+> macOS: if the binary is quarantined, run `xattr -d com.apple.quarantine ./weed` first.
+
+Perfect for development, testing, learning SeaweedFS, and single-node deployments.
 
 ## Quick Start for S3 API on Docker ##