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

server/lib/storage/payload.ts

@@ -0,0 +1,64 @@
+import type { Env } from "../types";
+
+const PAYLOAD_PREFIX = "webhooks/";
+const DEFAULT_TTL_SECONDS = 3600;
+
+export interface PayloadStore {
+  put(payload: string, ttl?: number): Promise<string>;
+  get(key: string): Promise<string | null>;
+  delete(key: string): Promise<void>;
+}
+
+function generateKey(): string {
+  const bytes = new Uint8Array(16);
+  crypto.getRandomValues(bytes);
+  const hex = Array.from(bytes)
+    .map((b) => b.toString(16).padStart(2, "0"))
+    .join("");
+  const now = new Date();
+  const y = now.getUTCFullYear();
+  const m = String(now.getUTCMonth() + 1).padStart(2, "0");
+  const d = String(now.getUTCDate()).padStart(2, "0");
+  return `${PAYLOAD_PREFIX}${y}/${m}/${d}/${hex}.json`;
+}
+
+export function r2PayloadStore(env: Env): PayloadStore {
+  const bucket = env.PAYLOAD;
+  if (!bucket) {
+    return {
+      async put(_payload: string): Promise<string> {
+        throw new Error("R2 binding is not configured");
+      },
+      async get(): Promise<null> {
+        throw new Error("R2 binding is not configured");
+      },
+      async delete(): Promise<void> {
+        throw new Error("R2 binding is not configured");
+      },
+    };
+  }
+
+  return {
+    async put(payload: string, ttl?: number): Promise<string> {
+      const key = generateKey();
+      const expires = new Date(
+        Date.now() + (ttl ?? DEFAULT_TTL_SECONDS) * 1000,
+      );
+      await bucket.put(key, payload, {
+        httpMetadata: { contentType: "application/json" },
+        customMetadata: { expires: expires.toISOString() },
+      });
+      return key;
+    },
+
+    async get(key: string): Promise<string | null> {
+      const obj = await bucket.get(key);
+      if (!obj) return null;
+      return obj.text();
+    },
+
+    async delete(key: string): Promise<void> {
+      await bucket.delete(key);
+    },
+  };
+}