fix: restore gateways to active set after long inactivity

[rickstaa]

Description

Ensure gateways which were inactive for >90 days are added to the active
set again so 30/60/90-day fee sums update.

Fixes # (issue)

Checklist

• Ran yarn prepare and verified yarn codegen and yarn build succeed.
• (Optional) Validated locally with yarn deploy:local.
• Confirmed the Subgraph Studio preview link in the PR comment works and the subgraph syncs without errors.

[github-actions]

🚀 Subgraph Studio preview deployed

Item	Details
Version label	pr-202-b67dbc4-20964667423
Query endpoint	https://api.studio.thegraph.com/query/31909/livepeer-ci/pr-202-b67dbc4-20964667423

curl -H 'Content-Type: application/json' \
  -d '{"query":"{ protocol(id: \"0\") { inflation } }"}' \
  https://api.studio.thegraph.com/query/31909/livepeer-ci/pr-202-b67dbc4-20964667423

[rickstaa]

This should have been already done in:

subgraph/utils/helpers.ts

Line 197 in cc648fd

let protocol = createOrLoadProtocol();

Not sure why it was not working without this logic.

[rickstaa]

This should have been already done in:

subgraph/utils/helpers.ts

Line 197 in cc648fd

let protocol = createOrLoadProtocol();

Not sure why it was not working without this logic.

I identified the issue: it was caused by creating and persisting two separate protocol objects. I removed the logic from the createOrLoadBroadcaster helper, since gateways should only be added to the activeBroadcasters array when they send fees.

This introduces some ambiguity around firstActiveDay. In the future, we could want to rename it to activationDay or firstFundedDay, but for now I have clarified the schema docstrings.

I opened #210 to track this and create a follow up pull request.