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/d00648d486ca_20251120202612.py

@@ -184,5 +184,5 @@ def downgrade() -> None:
     op.drop_table('end_users')
     op.drop_index(op.f('ix_retrieval_info_id'), table_name='retrieval_info')
     op.drop_table('retrieval_info')
-    op.drop_table('data_config')
+    op.execute('DROP TABLE IF EXISTS data_config')
     # ### end Alembic commands ###