refactor: eliminate string/magic-number literals (goconst, mnd) and fix const-type grouping (SA9004)

- upload/task: taskCategoryUpload/taskQueueDefault 常量替代 8 处字面量
- admin: 复用既有 logDBNameSQLite 常量替代 3 处 "sqlite" 字面量
- pkg/cache/disk: defaultCleanupInterval 命名常量
- driver_asynq_worker/executor: 分离 contextKey 类型常量组
lint_issues 45→34, tests 44/44

.golangci.yml

@@ -37,7 +37,6 @@ linters:
     dupl:
       threshold: 80
 
-
     cyclop:
       max-complexity: 20
       package-average: 10
@@ -59,11 +58,4 @@ linters:
 # 完整上报所有问题（取消 golangci 默认 50/3 截断，保证 code-check 与度量真实）
 issues:
   max-issues-per-linter: 0
-  max-same-issues: 0
-
-formatters:
-  enable:
-    - gofumpt
-  settings:
-    gofumpt:
-      extra-rules: true
+  max-same-issues: 0