Play Framework

chore(ci): modernize renovate config and enable fork processing (PF-153)

Prepares renovate.json5 for activation via the Mend-hosted Renovate app. The
config was written pre-Renovate-40 and, while Renovate still auto-migrated it
at load time, every run logged "Config migration necessary".

forkProcessing: "enabled" is the change that decides whether Renovate runs at
all here. tsukhani/play1 is a fork of playframework/play1, and Renovate skips
forks by default - including forks that carry a config file, since it cannot
tell whether the file came from upstream. Mend only enables fork processing
automatically for "Selected repositories" installs; an "All repositories"
install would leave this repo silently unprocessed. Setting it in-repo makes
activation independent of how the app is installed.

Syntax brought current:
  - fileMatch -> managerFilePatterns (renamed in v40; regex needs slash-wrapping)
  - matchPackagePrefixes -> matchPackageNames globs, 13 rules (removed in v40)
  - compound "after 10pm and before 5am every weekday" schedule split in two

The glob form uses "io.netty:**" rather than Renovate's literal migration
output "io.netty:{/,}**" - the brace alternation only matters for names
containing "/", which Maven coordinates never do. Verified against minimatch
that the prefix semantics are preserved, including the negative cases:
"io.nettyfoo:bar" is excluded, and "org.junit.**" does not match
"org.junit:junit".

renovate-config-validator now reports only "Config validated successfully",
with no migration warning.

Activation still requires installing the Mend app and enabling Issues (the
dependency dashboard is an Issue). Note the ticket's expected first-run PRs
(gradle-plugin JUnit 6.0.3, Gradle wrapper 9.5.0) are stale - both were fixed
manually in PF-151.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>