feat(api): enhance Actions Secrets Management API for repository (#30656)

- Add endpoint to list repository action secrets in API routes
- Implement `ListActionsSecrets` function to retrieve action secrets
from the database
- Update Swagger documentation to include the new
`/repos/{owner}/{repo}/actions/secrets` endpoint
- Add `actions` package import and define new routes for actions,
secrets, variables, and runners in `api.go`.
- Refactor action-related API functions into `Action` struct methods in
`org/action.go` and `repo/action.go`.
- Remove `actionAPI` struct and related functions, replacing them with
`NewAction()` calls.
- Rename `variables.go` to `action.go` in `org` directory.
- Delete `runners.go` and `secrets.go` in both `org` and `repo`
directories, consolidating their content into `action.go`.
- Update copyright year and add new imports in `org/action.go`.
- Implement `API` interface in `services/actions/interface.go` for
action-related methods.
- Remove individual action-related functions and replace them with
methods on the `Action` struct in `repo/action.go`.

---------

Signed-off-by: Bo-Yi Wu <appleboy.tw@gmail.com>
Signed-off-by: appleboy <appleboy.tw@gmail.com>
(cherry picked from commit 852547d0dc70299589c7bf8d00ea462ed709b8e5)

Conflicts:
	routers/api/v1/api.go
	trivial conflict because of Fix #2512 /api/forgejo/v1/version auth check (#2582)

templates/swagger/v1_json.tmpl

@@ -3711,6 +3711,54 @@
         }
       }
     },
+    "/repos/{owner}/{repo}/actions/secrets": {
+      "get": {
+        "produces": [
+          "application/json"
+        ],
+        "tags": [
+          "repository"
+        ],
+        "summary": "List an repo's actions secrets",
+        "operationId": "repoListActionsSecrets",
+        "parameters": [
+          {
+            "type": "string",
+            "description": "owner of the repository",
+            "name": "owner",
+            "in": "path",
+            "required": true
+          },
+          {
+            "type": "string",
+            "description": "name of the repository",
+            "name": "repo",
+            "in": "path",
+            "required": true
+          },
+          {
+            "type": "integer",
+            "description": "page number of results to return (1-based)",
+            "name": "page",
+            "in": "query"
+          },
+          {
+            "type": "integer",
+            "description": "page size of results",
+            "name": "limit",
+            "in": "query"
+          }
+        ],
+        "responses": {
+          "200": {
+            "$ref": "#/responses/SecretList"
+          },
+          "404": {
+            "$ref": "#/responses/notFound"
+          }
+        }
+      }
+    },
     "/repos/{owner}/{repo}/actions/secrets/{secretname}": {
       "put": {
         "consumes": [