add new functionality and improve backend server structure

- Enhance server functionality and optimize backend code
- Add multi-database support (PostgreSQL, MySQL, SQLite)

server/core_backend-server/golangci.yml

@@ -0,0 +1,26 @@
+version: "2"
+run:
+  concurrency: 4
+  timeout: 10m
+linters:
+  default: none
+  enable:
+    - asasalint
+    - asciicheck
+    - gomodguard
+    - goprintffuncname
+    - govet
+    - ineffassign
+    - misspell
+    - nakedret
+    - nolintlint
+    - prealloc
+    - reassign
+    - staticcheck
+    - unconvert
+    - unused
+    - whitespace
+formatters:
+  enable:
+    - gofmt
+    - goimports