fix(accounts): fix OpenAI OAuth usage quota never refreshing on manual refresh

The refresh button had no effect because two independent gates blocked
the Codex probe:

1. isOpenAICodexSnapshotStale returned false for non-WS-v2 accounts even
   when data was stale — this is correct for background auto-refresh (Codex
   quota is only auto-tracked for Codex CLI / WS v2 accounts), so this
   behavior is preserved.

2. shouldProbeOpenAICodexSnapshot had a 10-min in-memory rate limit with
   no bypass for explicit user requests.

Fix: add a force parameter threaded from handler → GetUsage → getOpenAIUsage
→ shouldProbeOpenAICodexSnapshot. When force=true (manual refresh button),
both gates are bypassed and the probe always runs. Background auto-loads
continue to respect the original WS v2 logic and 10-min rate limit.

backend/internal/handler/admin/account_handler.go

@@ -1643,7 +1643,7 @@ func (h *OAuthHandler) SetupTokenCookieAuth(c *gin.Context) {
 }
 
 // GetUsage handles getting account usage information
-// GET /api/v1/admin/accounts/:id/usage?source=passive|active
+// GET /api/v1/admin/accounts/:id/usage?source=passive|active&force=true
 func (h *AccountHandler) GetUsage(c *gin.Context) {
 	accountID, err := strconv.ParseInt(c.Param("id"), 10, 64)
 	if err != nil {
@@ -1652,12 +1652,13 @@ func (h *AccountHandler) GetUsage(c *gin.Context) {
 	}
 
 	source := c.DefaultQuery("source", "active")
+	force := c.Query("force") == "true"
 
 	var usage *service.UsageInfo
 	if source == "passive" {
 		usage, err = h.accountUsageService.GetPassiveUsage(c.Request.Context(), accountID)
 	} else {
-		usage, err = h.accountUsageService.GetUsage(c.Request.Context(), accountID)
+		usage, err = h.accountUsageService.GetUsage(c.Request.Context(), accountID, force)
 	}
 	if err != nil {
 		response.ErrorFrom(c, err)