Docs/installation tutorial (#7)

* [add]修改迁移文件新建空白表结构

* Add installation guide and environment setup

Added installation instructions and environment requirements for MemoryBear.

* [delete]删除api，web的readme.md。只保留唯一readme.md

* Fix database connection example in README

Update database connection configuration example in README.

api/migrations/versions/6e254c5f498e_20251125181327.py

@@ -20,14 +20,21 @@ depends_on: Union[str, Sequence[str], None] = None
 
 def upgrade() -> None:
     # ### commands auto generated by Alembic - please adjust! ###
-    op.alter_column('data_config', 'llm_id',
-               existing_type=sa.VARCHAR(),
-               comment='LLM模型配置ID',
-               existing_nullable=True)
-    op.alter_column('data_config', 'embedding_id',
-               existing_type=sa.VARCHAR(),
-               comment='嵌入模型配置ID',
-               existing_nullable=True)
+    # 检查表和列是否存在再进行操作
+    op.execute("""
+        DO $$
+        BEGIN
+            IF EXISTS (SELECT FROM information_schema.columns 
+                      WHERE table_name = 'data_config' AND column_name = 'llm_id') THEN
+                COMMENT ON COLUMN data_config.llm_id IS 'LLM模型配置ID';
+            END IF;
+            
+            IF EXISTS (SELECT FROM information_schema.columns 
+                      WHERE table_name = 'data_config' AND column_name = 'embedding_id') THEN
+                COMMENT ON COLUMN data_config.embedding_id IS '嵌入模型配置ID';
+            END IF;
+        END $$;
+    """)
     op.add_column('workspaces', sa.Column('storage_type', sa.String(), nullable=True))
     # ### end Alembic commands ###