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>

README.md

@@ -200,8 +200,7 @@ CREATE TABLE correlated_logs_http_network (
     dst_port UInt32,
     correlated UInt8,
     orphan_side String,
-    apache JSON,
-    network JSON
+    fields JSON
 ) ENGINE = MergeTree()
 ORDER BY (timestamp, src_ip, src_port);
 ```