docs: add multi-language documentation (ru, fa, zh, tr, ar)

docs/zh/vector.md

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+# 向量搜索引擎
+
+用于相似性搜索的本机 HNSW 和 IVF-PQ 索引。
+
+## 用法
+
+```nim
+import barabadb/vector/engine
+
+var idx = newHNSWIndex(dimensions = 128)
+idx.insert(1, @[1.0'f32, 0.0'f32, ...], {"category": "A"}.toTable)
+
+let results = idx.search(queryVector, k = 10)
+```
+
+## 索引类型
+
+### HNSW
+
+用于近似最近邻搜索的分层可导航小世界图。
+
+```nim
+var hnsw = newHNSWIndex(
+  dimensions = 128,
+  m = 16,
+  efConstruction = 200,
+  efSearch = 100
+)
+```
+
+### IVF-PQ
+
+带乘积量化的倒排文件索引。
+
+```nim
+var ivfpq = newIVFPQIndex(
+  dimensions = 128,
+  numCentroids = 256,
+  subQuantizers = 8
+)
+```
+
+## 距离度量
+
+| 度量 | 描述 |
+|------|------|
+| `cosine` | 余弦相似度 |
+| `euclidean` | L2 距离 |
+| `dotproduct` | 点积相似度 |
+| `manhattan` | L1 距离 |
+
+## 量化
+
+```nim
+let scalar = scalarQuantize(data, bits = 8)
+let pq = productQuantize(data, subVectors = 8, bits = 8)
+```
+
+## SIMD 加速
+
+```nim
+import barabadb/vector/simd
+
+let dist = simdCosineDistance(vec1, vec2)
+```