Code structure refactor — split large files

[linear]

Split 5 oversized files into focused modules. No behavior changes — only file organization.

• manageNodeCall.ts (1007 lines, 45 switch cases) → network/handlers/ by domain (blocks, txs, peers, identity, tlsnotary, l2ps)
• GCRIdentityRoutines.ts (2194 lines, 19 routines) → separate files per domain (web2, web3, pqc, attestation, zk, rewards)
• chain.ts (781 lines, 33 methods) → chainBlocks.ts, chainTransactions.ts, chainGenesis.ts, chainDb.ts with Chain as facade
• server_rpc.ts (741 lines) → routes/ by domain (node, peer, zk, genesis, monitoring)
• endpointHandlers.ts (891 lines, 14 handlers) → handlers/ by domain (l2ps, crosschain, tx, consensus, state)