feat: release v1.0.3 with flattened JSON output structure

- breaking: remove apache and network subdivisions from JSON output
- feat: all log fields now merged into single-level JSON structure
- feat: custom MarshalJSON() implementation for flat output
- chore: update ClickHouse schema to use single fields JSON column
- docs: update CHANGELOG.md and README.md with v1.0.3 changes
- build: bump version to 1.0.3 in build.sh and RPM spec

Migration notes:
- Existing ClickHouse tables need schema migration to use fields JSON column
- Replace apache JSON and network JSON columns with fields JSON column

Co-authored-by: Qwen-Coder <qwen-coder@alibabacloud.com>

build.sh

@@ -5,7 +5,7 @@ set -e
 SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
 cd "$SCRIPT_DIR"
 
-VERSION="${VERSION:-1.0.2}"
+VERSION="${VERSION:-1.0.3}"
 OUTPUT_DIR="${SCRIPT_DIR}/dist"
 
 echo "=============================================="