Refactor config, payments, websocket, and routing

[distributed-nerd]

Summary

• Add environment-specific app/backend config validation
• Introduce multi-chain payment and wallet strategy routing
• Refactor websocket notifications around an event bus
• Enable lazy route loading and chunk prefetching

Verification

• Targeted frontend coverage: 87.8% lines overall for changed frontend files
• Backend changed-file coverage: 88.34% lines overall; PaymentRouter.ts at 100%
• Targeted lint: clean
• Prettier check: clean
• git diff --check: clean
• npm run performance:ci: passed
• npm run typecheck: still fails on existing project-wide baseline issues unrelated to this branch

Closes #978
Closes #975
Closes #979
Closes #977

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GitGuardian id	GitGuardian status	Secret	Commit	Filename
-	-	Generic High Entropy Secret	fba114d	src/services/tests/walletChainStrategies.test.ts	View secret

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