Centralize network and deployment capability configuration

[egekoca]

Summary

• add one typed capability matrix for the active network, RPC, explorer, CommunityFactory, legacy contracts, and proposal discovery
• replace ambiguous passphrase fields and migrate wallet, guards, contract clients, deployment, registry, health, scripts, docs, and shared fixtures
• represent unavailable deployment capabilities explicitly with actionable environment requirements
• pass public configuration to the browser through a statically analyzable Next.js environment snapshot
• make health output capability-aware without leaking endpoint or contract values
• consolidate deterministic browser fixtures and update stale multi-community coverage to current canonical ID routes

Reliability and compatibility

• testnet retains the public RPC fallback; mainnet RPC remains explicit
• compatibility helpers stay available while all active consumers use named capability requirements
• production builds fail closed when an E2E fixture flag is present
• wallet signing, network comparison, proposal discovery, and deployment all consume the same network passphrase

Verification

• npm ci --ignore-scripts --no-audit --no-fund
• npm test — 442 Vitest + 6 production-health tests
• npm run test:e2e:ci — 30 Playwright tests across desktop and mobile
• npm run lint
• npm run typecheck
• npm run build
• git diff --check

Closes #254

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