hotfix: use all rpcs, update config, sdk

[hpihkala]

• Use all RPCs from @streamr/config instead of just the first one
• Update @streamr/config and @streamr/sdk packages
• npm update @ensdomains/buffer --package-lock-only to fix build issue related to disappeared npm package

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Note

• Use all RPCs in client config: getClientConfig now maps all chainConfig.rpcEndpoints to contracts.rpcs (as { url } objects) instead of using only the first endpoint
• Dependency updates: Bump @streamr/config to ^5.9.2 and @streamr/sdk to ^103.2.0
• Test environment shims: Add Jest mocks to use browser-friendly WebRTC implementation and @streamr/utils getSubtle via crypto.webcrypto.subtle to stabilize jsdom tests

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