refactor: 拆分 module.py 为 components 子包

- rope/linear/norm/embedding/mlp/attention/decoder_block 各自独立文件
- 依赖单向无循环
- 公开接口不变，外部无需修改

astrai/model/components/embedding.py

@@ -0,0 +1,13 @@
+import torch
+import torch.nn as nn
+import torch.nn.functional as F
+from torch import Tensor
+
+
+class Embedding(nn.Module):
+    def __init__(self, vocab_size: int, embedding_dim: int):
+        super().__init__()
+        self.weight = nn.Parameter(torch.empty((vocab_size, embedding_dim)))
+
+    def forward(self, x: Tensor) -> Tensor:
+        return F.embedding(x, self.weight)