[PT1-153] Update hardhat config for Etherscan API v2 from deprecated v1 (env change required)

[zZoMROT]

Static Code Analysis (readability, compactness):

Replaces Etherscan API network keys with a single v2 key. Config is simpler and easier to maintain.

Dynamic Code Analysis (external APIs, interaction flows):

Switches verification to Etherscan API v2.
Breaking: requires a new unified env var ETHERSCAN_API_KEY for method registerAll() for the API V2 key. API V1 keys no longer work (Etherscan sunset).

Efficiency (gas costs, computational complexity, memory requirements):

No runtime impact, configuration-only change.

Opinion, trade-offs and other thoughts (optional):

Breaking in contract source verifications (and deploys with verification) but necessary.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (10927a4) to head (4cabb9e).
⚠️ Report is 3 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff            @@
##            master      #201   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files           17        17           
  Lines          346       346           
  Branches        65        65           
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  Hits           346       346           

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[Sunnesoft]

Do we need to update hardhat packages to work with new etherscan API? Or its enough just to update API-key?

[zZoMROT]

Do we need to update hardhat packages to work with new etherscan API? Or its enough just to update API-key?

For now it’s enough to just update the API key and etherscan: apiKey hardhat config