feat(sns): 增强朋友圈时间线/媒体获取与实时同步

- 新增 /api/sns/users：按发圈数统计联系人（支持 keyword/limit）
- 新增 /api/sns/realtime/sync_latest：WCDB 实时增量同步到解密库（append-only），并持久化 sync state
- 朋友圈媒体优先走“远程下载+解密”：图片支持 wcdb_decrypt_sns_image，视频/实况支持 ISAAC64（WeFlow 逻辑）
- 增加 WeFlow WASM keystream(Node) 优先 + Python ISAAC64 fallback，提升兼容性
- wcdb_api.dll 支持多路径自动发现/环境变量覆盖，并在状态信息中回传实际使用路径

src/wechat_decrypt_tool/isaac64.py

@@ -0,0 +1,169 @@
+from __future__ import annotations
+
+"""ISAAC-64 PRNG (WeFlow compatible).
+
+WeChat SNS live photo/video decryption uses a keystream generated by ISAAC-64 and
+XORs the first 128KB of the mp4 file. WeFlow's implementation reverses the
+generated byte array, so we mirror that behavior for compatibility.
+"""
+
+from typing import Any
+
+_MASK_64 = 0xFFFFFFFFFFFFFFFF
+
+
+def _u64(v: int) -> int:
+    return int(v) & _MASK_64
+
+
+class Isaac64:
+    def __init__(self, seed: Any):
+        seed_text = str(seed).strip()
+        if not seed_text:
+            seed_val = 0
+        else:
+            try:
+                # WeFlow seeds with BigInt(seed), where seed is usually a decimal string.
+                seed_val = int(seed_text, 0)
+            except Exception:
+                seed_val = 0
+
+        self.mm = [_u64(0) for _ in range(256)]
+        self.aa = _u64(0)
+        self.bb = _u64(0)
+        self.cc = _u64(0)
+        self.randrsl = [_u64(0) for _ in range(256)]
+        self.randrsl[0] = _u64(seed_val)
+        self.randcnt = 0
+        self._init(True)
+
+    def _init(self, flag: bool) -> None:
+        a = b = c = d = e = f = g = h = _u64(0x9E3779B97F4A7C15)
+
+        def mix() -> tuple[int, int, int, int, int, int, int, int]:
+            nonlocal a, b, c, d, e, f, g, h
+            a = _u64(a - e)
+            f = _u64(f ^ (h >> 9))
+            h = _u64(h + a)
+
+            b = _u64(b - f)
+            g = _u64(g ^ _u64(a << 9))
+            a = _u64(a + b)
+
+            c = _u64(c - g)
+            h = _u64(h ^ (b >> 23))
+            b = _u64(b + c)
+
+            d = _u64(d - h)
+            a = _u64(a ^ _u64(c << 15))
+            c = _u64(c + d)
+
+            e = _u64(e - a)
+            b = _u64(b ^ (d >> 14))
+            d = _u64(d + e)
+
+            f = _u64(f - b)
+            c = _u64(c ^ _u64(e << 20))
+            e = _u64(e + f)
+
+            g = _u64(g - c)
+            d = _u64(d ^ (f >> 17))
+            f = _u64(f + g)
+
+            h = _u64(h - d)
+            e = _u64(e ^ _u64(g << 14))
+            g = _u64(g + h)
+            return a, b, c, d, e, f, g, h
+
+        for _ in range(4):
+            mix()
+
+        for i in range(0, 256, 8):
+            if flag:
+                a = _u64(a + self.randrsl[i])
+                b = _u64(b + self.randrsl[i + 1])
+                c = _u64(c + self.randrsl[i + 2])
+                d = _u64(d + self.randrsl[i + 3])
+                e = _u64(e + self.randrsl[i + 4])
+                f = _u64(f + self.randrsl[i + 5])
+                g = _u64(g + self.randrsl[i + 6])
+                h = _u64(h + self.randrsl[i + 7])
+            mix()
+            self.mm[i] = a
+            self.mm[i + 1] = b
+            self.mm[i + 2] = c
+            self.mm[i + 3] = d
+            self.mm[i + 4] = e
+            self.mm[i + 5] = f
+            self.mm[i + 6] = g
+            self.mm[i + 7] = h
+
+        if flag:
+            for i in range(0, 256, 8):
+                a = _u64(a + self.mm[i])
+                b = _u64(b + self.mm[i + 1])
+                c = _u64(c + self.mm[i + 2])
+                d = _u64(d + self.mm[i + 3])
+                e = _u64(e + self.mm[i + 4])
+                f = _u64(f + self.mm[i + 5])
+                g = _u64(g + self.mm[i + 6])
+                h = _u64(h + self.mm[i + 7])
+                mix()
+                self.mm[i] = a
+                self.mm[i + 1] = b
+                self.mm[i + 2] = c
+                self.mm[i + 3] = d
+                self.mm[i + 4] = e
+                self.mm[i + 5] = f
+                self.mm[i + 6] = g
+                self.mm[i + 7] = h
+
+        self._isaac64()
+        self.randcnt = 256
+
+    def _isaac64(self) -> None:
+        self.cc = _u64(self.cc + 1)
+        self.bb = _u64(self.bb + self.cc)
+
+        for i in range(256):
+            x = self.mm[i]
+            if (i & 3) == 0:
+                # aa ^= ~(aa << 21)
+                self.aa = _u64(self.aa ^ (_u64(self.aa << 21) ^ _MASK_64))
+            elif (i & 3) == 1:
+                self.aa = _u64(self.aa ^ (self.aa >> 5))
+            elif (i & 3) == 2:
+                self.aa = _u64(self.aa ^ _u64(self.aa << 12))
+            else:
+                self.aa = _u64(self.aa ^ (self.aa >> 33))
+
+            self.aa = _u64(self.mm[(i + 128) & 255] + self.aa)
+            y = _u64(self.mm[(x >> 3) & 255] + self.aa + self.bb)
+            self.mm[i] = y
+            self.bb = _u64(self.mm[(y >> 11) & 255] + x)
+            self.randrsl[i] = self.bb
+
+    def get_next(self) -> int:
+        if self.randcnt == 0:
+            self._isaac64()
+            self.randcnt = 256
+        idx = 256 - self.randcnt
+        self.randcnt -= 1
+        return _u64(self.randrsl[idx])
+
+    def generate_keystream(self, size: int) -> bytes:
+        """Generate a keystream of `size` bytes (must be multiple of 8)."""
+        if size <= 0:
+            return b""
+        if size % 8 != 0:
+            raise ValueError("ISAAC64 keystream size must be multiple of 8 bytes.")
+
+        out = bytearray()
+        count = size // 8
+        for _ in range(count):
+            out.extend(int(self.get_next()).to_bytes(8, "little", signed=False))
+
+        # WeFlow reverses the entire byte array (Uint8Array.reverse()).
+        out.reverse()
+        return bytes(out)
+