Standardize polling

[Randy808]

To alleviate the burden on user rate limits, I reduced the polling cadence for some endpoints to something more manageable (and standardized polling intervals in const.js).

Here's a summary of the changes:

• Standardized global chain-tip polling at 30s, while retaining navigation-triggered refreshes on block, transaction, and address pages, rate-limited to at most
  once every 5s
• Changed recent mempool transaction polling from 5s to 30s
• Changed mempool summary polling from 30s to 60s on mempool and unconfirmed-transaction pages
• Changed fee-estimate polling to 60s on mempool, recent-transactions, and unconfirmed-transaction pages
• Changed block-list refreshes to be tip-triggered, with a 10-minute fallback for same-height reorgs
• Replaced timed confirmed-peg polling with block-triggered requests; retained 60s polling for pending peg transactions
• Changed market chart refreshes from 60s to 10 minutes
• Changed high-value asset refreshes from 60s to 10 minutes

---

To run locally, npm install and use the following snippets:

# Bitcoin
export API_URL=https://blockstream.info/api
export PORT=4999
source flavors/blockstream/config.env
source flavors/bitcoin-mainnet/config.env
npm run dev-server

# Liquid
export API_URL=https://blockstream.info/liquid/api
export PORT=5000
source flavors/blockstream/config.env
source flavors/liquid-mainnet/config.env
npm run dev-server