Add Pino logging to governance API

[lukozill]

Summary

Introduces structured JSON logging across the governance-api service using
pino and pino-http, replacing all unstructured console.log/console.info
calls. This makes incident investigation possible by capturing every
significant runtime event with enough context to diagnose failures without
reproduction.

Changes

• lib/logger.ts — new shared pino logger singleton used throughout
  the service.
• lib/app.ts — installs pino-http middleware; responses with HTTP
  status ≥ 400 are logged at error level, all others at info.
• lib/server.ts — startup is wrapped in try/catch; DB sync and
  successful bind emit logger.info; any startup failure emits
  logger.error and exits with code 1.
• lib/routes/message.ts — every validation-failure 400 path now
  emits log.error with an error_code field before responding; each
  successful processing step (signature verified, liquidity fetched, DB
  record created) emits log.info; final console.log replaced.
• lib/routes/spaces.ts — both async route handlers wrapped in
  try/catch; DB errors emit logger.error and return a 500 instead of an
  unhandled promise rejection.
• lib/utils/pin-ipfs.ts — IPFS pin success logged at info for
  both Pinata and local-node paths; pin failure logged at error before
  throwing.
• lib/zilliqa/custom-fetch.ts — Zilliqa RPC call wrapped in
  try/catch with error log on failure; successful liquidity fetch logged
  at info; XCAD and ZilSwap parse errors use logger.error instead of
  console.log.
• package.json — adds pino and pino-http as runtime deps;
  pino-pretty and @types/pino-http as dev deps; TypeScript bumped to
  3.9.x.

Test plan

• Start the service in Docker and confirm it boots without errors and
  emits a structured "Server started" log line.
• Submit a valid proposal via POST /api/message and confirm that adequate message appear in logs.
• Hit GET /api/:space/proposals and confirm the request is logged by
  pino-http.