feat(supply-api): 完成核心模块实现

新增/修改内容：
- config: 添加配置管理（config.example.yaml, config.go）
- cache: 添加Redis缓存层（redis.go）
- domain: 添加invariants不变量验证及测试
- middleware: 添加auth认证和idempotency幂等性中间件及测试
- repository: 添加完整数据访问层（account, package, settlement, idempotency, db）
- sql: 添加幂等性表DDL脚本

代码覆盖：
- auth middleware实现凭证边界验证
- idempotency middleware实现请求幂等性
- invariants实现业务不变量检查
- repository层实现完整的数据访问逻辑

关联issue: Round-1 R1-ISSUE-006 凭证边界硬门禁

supply-api/config/config.example.yaml

@@ -0,0 +1,37 @@
+# Supply API Development Configuration
+server:
+  addr: ":18082"
+  read_timeout: 10s
+  write_timeout: 15s
+  idle_timeout: 30s
+  shutdown_timeout: 5s
+
+database:
+  host: "localhost"
+  port: 5432
+  user: "postgres"
+  password: ""
+  database: "supply_db"
+  max_open_conns: 25
+  max_idle_conns: 5
+  conn_max_lifetime: 1h
+  conn_max_idle_time: 10m
+
+redis:
+  host: "localhost"
+  port: 6379
+  password: ""
+  db: 0
+  pool_size: 10
+
+token:
+  secret_key: "${SUPPLY_TOKEN_SECRET_KEY}"
+  issuer: "lijiaoqiao/supply-api"
+  access_token_ttl: 1h
+  refresh_token_ttl: 168h
+  revocation_cache_ttl: 30s
+
+audit:
+  buffer_size: 1000
+  flush_interval: 5s
+  export_timeout: 30s