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/guide/routes.md

@@ -1,6 +1,6 @@
 # Routes & Targets
 
-Routes define which events get forwarded to which channel (Discord or Telegram). They are stored in Cloudflare KV under the key `config:routes` as a JSON array, managed via the [Web UI](./configuration#web-ui), the [Admin API](../api/admin), or `config.example.yaml`.
+Routes define which events get forwarded to which channel (Discord or Telegram). They are stored in D1 (`d1_routes`, seeded from the legacy KV `config:routes` key on first load), managed via the [Web UI](./configuration#web-ui), the [Admin API](../api/admin), or `config.example.yaml`.
 
 There are **no default routes** — each route must define its own target. If no routes are configured, no events are forwarded. At most **200 routes** can be saved per instance.