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/configuration.md

@@ -60,7 +60,7 @@ WebHooker ships with a built-in config console at `/admin` for managing routes,
 
 The console is served as an SPA at `/admin`; its tabs are deep-linkable via the URL path (`/admin/groups`, `/admin/logs`, `/admin/audit`). URLs outside `/admin` that do not match an endpoint return a plain `404` instead of the console.
 
-All management endpoints (`/admin/api/*`) are documented in the [Admin API](../api/admin). Saved routes are written to KV `config:routes` immediately and the config cache is invalidated so the webhook pipeline picks them up on the next run.
+All management endpoints (`/admin/api/*`) are documented in the [Admin API](../api/admin). Saved routes and groups are persisted to D1 (`d1_routes` / `d1_groups`) immediately, the KV cache is invalidated and the config cache is refreshed so the webhook pipeline picks them up on the next run.
 
 ## Filter Types