feat(storage): migrate config, dedup and delivery state to D1

- Move oversized queue payloads from KV to R2 (PAYLOAD binding, webhooks/YYYY/MM/DD/*.json, KV queue:payload:* fallback)
- Persist routes/groups to D1 (d1_routes/d1_groups) with memory -> KV -> D1 three-tier cache, seeded from legacy KV config keys
- Move webhook dedup (dedup_keys), delivery state (delivery_state) and message tracking (message_tracking) to D1 via canUseD1 probe with automatic KV fallback
- Batch send_logs inserts (recordSendBatch) and add group_id/ts index
- Add storage-prune scheduled task for expired dedup/state/tracking rows
- Add TTL to invite:group:{id} index and audit all ephemeral KV keys
- Add D1 indexes for the new tables
- Sync AGENTS.md, README.md/zh and docs/ (en/zh) with the new storage layout

docs/zh/guide/faq.md

@@ -34,4 +34,4 @@
 
 ## 数据存储在哪里？
 
-配置存于 Cloudflare KV（`config:routes`、`config:groups`）；发送/审计日志与平台↔GitHub 绑定存于 D1。见[存储布局](./storage#kv-存储布局)。
+配置存于 D1（`d1_routes`/`d1_groups`，KV 仅作缓存）；webhook 去重、投递状态与消息更新追踪同样存于 D1（KV 回退）；发送/审计日志与平台↔GitHub 绑定存于 D1；超大负载可选存于 R2。见[存储布局](./storage#存储决策)。