Add Panchain (PC) native currency price feed - Chain ID 7890

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### What is this about?

## Request: Add Native Coin Price Feed for Panchain Network

Please add native coin price feed support for Panchain network in MetaMask.

**Chain Details:**
- Chain Name: Panchain Mainnet
- Chain ID: 7890
- Native Currency: PC (Pan Coin)
- RPC URL: https://publicrpc.panchain.io
- Explorer: https://scan.panchain.io
- Website: https://panchain.io

**Price Feed:**
- CoinGecko URL: https://coingecko.com/en/coins/panchain
- CoinGecko API ID: panchain
- Current Price: ~$2,721

**Notes:**
- PC is a native L1 coin (not a token), no contract address
- Chain is listed on chainlist.org (Chain ID 7890)
- ethereum-lists/chains PR #8113 submitted

### Scenario

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### Design

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### Technical Details

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### Threat Modeling Framework

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### Acceptance Criteria

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### Stakeholder review needed before the work gets merged

- [ ] Engineering (needed in most cases)
- [ ] Design
- [ ] Product
- [ ] QA (automation tests are required to pass before merging PRs but not all changes are covered by automation tests - please review if QA is needed beyond automation tests)
- [ ] Security
- [ ] Legal
- [ ] Marketing
- [ ] Management (please specify)
- [ ] Other (please specify)

### References

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The issue names no files, tests, or entry points. Start by locating existing native-currency price-feed integrations and their CoinGecko mappings, then compare how chain ID 7890 is represented. Done means Panchain's PC price is displayed correctly and the relevant automated tests pass.

Written by the indexing model from the issue text.