chore: exactly match the list licenses v2 structure with FF on

[vikrantgupta25]

Summary

• the plan key in the new structure was missing PLAN in the string end
• added the valid until of 1 year similar to previous flow

Related Issues / PR's

Screenshots

NA

Affected Areas and Manually Tested Areas

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[!IMPORTANT] Align license structure with feature flag by mapping old plan keys to new names and setting default validity in license.go and manager.go.

• Behavior:
  • In convertLicenseV3ToLicenseV2 in license.go, map old plan keys to new plan names using MapOldPlanKeyToNewPlanName.
  • In GetLicensesV3 in manager.go, set ValidUntil to one year from ValidFrom if ValidUntil is -1.
• Models:
  • Add MapOldPlanKeyToNewPlanName in plans.go to map old plan keys to new plan names.
• Misc:
  • Ensure PlanKey in LicensePlan is correctly set in convertLicenseV3ToLicenseV2.

^{This description was created by for ba2e84bf0d840834dbc1863580a709b79ab2da5f. It will automatically update as commits are pushed.}

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[vikrantgupta25]

contributes to - https://github.com/SigNoz/platform-pod/issues/325