chore: add t-tooling label to new PRs as well

[vladfrangu]

Extends the new-issue labeling workflow to also run on PR open, adding the t-tooling label. Replicates apify/crawlee#4222.

• Uses pull_request_target so the token can write labels on PRs from forks (nothing is checked out, so this is safe).
• Adds pull-requests: write permission. context.issue.number already resolves to the PR number for PR events.

[🤖] Claude Code using Opus 5.5

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.46%. Comparing base (6ab27de) to head (3c81c15).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1116   +/-   ##
=======================================
  Coverage   95.46%   95.46%           
=======================================
  Files          61       61           
  Lines        5935     5935           
=======================================
  Hits         5666     5666           
  Misses        269      269           

Flag	Coverage Δ
integration	90.66% <ø> (+0.06%)	⬆️
unit	88.87% <ø> (ø)

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[vdusek]

LGTM