[Platform API] Maintainability & Code Quality

func requireOrgID(w http.ResponseWriter, r *http.Request) (string, bool) {
	orgID, ok := middleware.GetOrganizationFromRequest(r)
	if !ok {
		httputil.WriteJSON(w, http.StatusUnauthorized, utils.NewErrorResponseWithCode(
			utils.CodeCommonUnauthorized, "Organization claim not found in token"))
		return "", false
	}
	return orgID, true
}

Then each handler becomes:

-	orgID, ok := middleware.GetOrganizationFromRequest(r)
-	if !ok {
-		httputil.WriteJSON(w, http.StatusUnauthorized, utils.NewErrorResponseWithCode(
-			utils.CodeCommonUnauthorized, "Organization claim not found in token"))
-		return
-	}
+	orgID, ok := requireOrgID(w, r)
+	if !ok {
+		return
+	}

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@platform-api/internal/handler/llm.go` around lines 110 - 115, The org-claim
authorization check is duplicated across multiple LLM handlers, causing repeated
Unauthorized response logic and risking drift. Add a shared helper in llm.go,
such as requireOrgID, that wraps middleware.GetOrganizationFromRequest and
returns the org ID or writes the CodeCommonUnauthorized JSON error with the same
message. Update each handler in llm.go and the related copies in llm_apikey.go,
llm_deployment.go, and llm_proxy_apikey.go to call this helper instead of
inlining the block.