feat(conf): 支持 TOML 配置文件格式

- 替换 serde_ini 为 toml crate，直接反序列化到强类型结构体
- 删除 300+ 行手写 match 解析逻辑
- 支持 [raft] TOML section 原生语法
- memory 字段支持 "1GB" 字符串和整数两种写法
- 错误信息带行号定位
- 更新 kiwi.conf 为 TOML 格式
- 新增 4 个测试覆盖 raft section、memory 字符串/整数、最小配置

closes #247

Author: AlexStocks

.ai-team/design-docs/toml-config-design-20260527.md

@@ -0,0 +1,83 @@
+# TOML Configuration Support — Design Doc
+
+**Issue:** #247 — Add proper TOML configuration file support
+**Date:** 2026-05-27
+**Status:** Approved
+
+## Problem
+
+Current config system uses a hand-rolled Redis-style parser (`parse_redis_config`) that:
+- Only handles `key = value` and `key value` format
+- Cannot parse TOML sections (`[raft]`), arrays, or nested structures
+- All values are parsed as strings, then manually converted
+- The existing `config.example.toml` uses TOML format that the parser cannot read
+
+## Solution
+
+Replace the manual parser with the `toml` crate + serde `Deserialize`:
+
+### TOML Structure
+
+```toml
+# Basic
+binding = "127.0.0.1"
+port = 7379
+timeout = 300
+memory = "1GB"
+log-dir = "./logs"
+db-dir = "./db"
+db-path = ""
+db-instance-num = 3
+redis-compatible-mode = true
+# requirepass = "secret"
+
+# Compaction
+small-compaction-threshold = 10
+small-compaction-duration-threshold = 180
+
+# RocksDB
+rocksdb-max-subcompactions = 1
+rocksdb-max-background-jobs = 2
+rocksdb-max-write-buffer-number = 2
+rocksdb-min-write-buffer-number-to-merge = 1
+rocksdb-write-buffer-size = 67108864
+rocksdb-level0-file-num-compaction-trigger = 4
+rocksdb-num-levels = 7
+rocksdb-enable-pipelined-write = false
+rocksdb-level0-slowdown-writes-trigger = 20
+rocksdb-level0-stop-writes-trigger = 36
+rocksdb-ttl-second = 0
+rocksdb-periodic-second = 0
+rocksdb-level-compaction-dynamic-level-bytes = false
+rocksdb-max-open-files = 10000
+rocksdb-target-file-size-base = 67108864
+rocksdb-compression-type = "lz4"
+
+# Raft (optional section)
+[raft]
+node-id = 1
+raft-addr = "127.0.0.1:9220"
+resp-addr = "127.0.0.1:7379"
+data-dir = "./raft-data"
+# heartbeat-interval-ms = 500
+# election-timeout-min-ms = 1500
+# election-timeout-max-ms = 3000
+use-memory-log-store = false
+```
+
+### Key Design Decisions
+
+1. **Flat top-level keys** — RocksDB settings stay flat (not nested under `[rocksdb]`) to minimize migration friction
+2. **`[raft]` section** — Uses TOML table syntax, maps to `Option<RaftClusterConfig>`
+3. **`memory` field** — Keep string format ("1GB") with custom serde deserializer (`deserialize_memory`)
+4. **Backward compat** — Drop Redis-style format entirely (it was never a real parser)
+5. **Error messages** — `toml` crate gives line/column numbers in errors
+
+### Files to Modify
+
+| File | Change |
+|------|--------|
+| `src/conf/Cargo.toml` | Add `toml = "0.8"` |
+| `src/conf/src/config.rs` | Add `Deserialize` derive + serde attrs, rewrite `Config::load()` |
+| `src/conf/src/de_func.rs` | Keep `deserialize_memory`/`deserialize_bool_from_yes_no`, remove `parse_redis_config`/`parse_config_line`/`redis_config_to_ini` |
+| `src/conf/src/lib.rs` | Update tests to use TOML format |

Cargo.lock

@@ -8,7 +8,7 @@ workspace = true
 
 [dependencies]
 serde = { version = "1.0", features = ["derive"] }
-serde_ini = "0.2.0"
+toml = "0.8"
 validator = { version = "0.20", features = ["derive"] }
 snafu = "0.8.5"
 rocksdb.workspace = true