ccm,ocm: improve balancer least_used with plan-weighted scoring and reset urgency

Scale remaining capacity by plan weight (Pro=1, Max 5x=5, Max 20x=10
for CCM; Plus=1, Pro=10 for OCM) so higher-tier accounts contribute
proportionally more. Factor in weekly reset proximity so credentials
about to reset are preferred ("use it or lose it").

Auto-detect plan weight from subscriptionType + rateLimitTier (CCM)
or plan_type (OCM). Fetch /api/oauth/profile when rateLimitTier is
missing from the credential file. External credentials accept a
manual plan_weight option.

option/ccm.go

@@ -102,6 +102,7 @@ type CCMExternalCredentialOptions struct {
 	Token        string             `json:"token"`
 	Reverse      bool               `json:"reverse,omitempty"`
 	Detour       string             `json:"detour,omitempty"`
+	PlanWeight   float64            `json:"plan_weight,omitempty"`
 	UsagesPath   string             `json:"usages_path,omitempty"`
 	PollInterval badoption.Duration `json:"poll_interval,omitempty"`
 }

option/ocm.go

@@ -102,6 +102,7 @@ type OCMExternalCredentialOptions struct {
 	Token        string             `json:"token"`
 	Reverse      bool               `json:"reverse,omitempty"`
 	Detour       string             `json:"detour,omitempty"`
+	PlanWeight   float64            `json:"plan_weight,omitempty"`
 	UsagesPath   string             `json:"usages_path,omitempty"`
 	PollInterval badoption.Duration `json:"poll_interval,omitempty"`
 }