refactor: reorganize project structure and update configurations

- Move migrations/ to database/schema/ for clarity on database schema definitions
- Move sqlc.yaml to internal/database/ to group with database code
- Move static/ to cmd/server/static/ to co-locate with server
- Update all configuration files and documentation
- Follow Go project conventions for better organization

bruno/user/Add Ebook Folder.bru

@@ -12,7 +12,7 @@ post {
 
 body:json {
   {
-    "folder_path": "/home/user/ebooks"
+    "folder_path": "/app/uploads"
   }
 }
 
@@ -46,4 +46,4 @@ docs {
   - 400: Invalid request
   - 401: Unauthorized
   - 409: Folder already exists
-}
+}