chore: prepare release 0.2.0

[github-actions]

This PR was created automatically. Merging it will finalize the changelog for 0.2.0

Breaking Changes

• Replaced POST /system/sqlite3/backup with POST /snapshots

Features

Add log flags

-log.file.enabled and -log.stdout.enableANSI set the two log options from the
command line, so a service manager that already captures stdout can turn off the
log file and the color codes without editing the config file. Neither default
changed.

Make redundancy configurable

sia.dataShards and sia.parityShards set the erasure coding scheme used for
uploads, defaulting to the previous 10 of 30. An invalid combination is rejected
before s3d opens its listeners or database. Objects already stored keep their
original scheme and remain readable.

Validate X-Amz-Checksum-* request headers

PutObject now verifies the CRC32, CRC32C, CRC64NVME, MD5, SHA1,
SHA256 and SHA512 checksum headers rather than storing them unchecked, and
refuses a mismatch with BadDigest. A request naming more than one checksum is
refused with InvalidRequest. Checksums sent as streaming X-Amz-Trailer
values are verified the same way, which they previously were not.

Fixes

Filter request headers from object metadata

Object writes now store only object metadata headers. Request control headers
such as signing, copy, tagging, ACL and encryption headers are no longer saved
as metadata or replayed on later reads, and metadata stored by earlier versions
is filtered when an object is read. A migration prunes it from the database so
a later CopyObject does not carry it forward. Content-Language is now stored
and returned with the object, which it previously was not.

Sync the upload directory after staging an object

Staged uploads were written and synced, but the directory holding them was
not, so an unclean shutdown could leave the database referencing a file that
no longer had a directory entry.