feat(server): expose error tracking config and captureException options

[cat-ph]

💡 Motivation and Context

Second PR in the 4-PR JVM error-tracking stack. It exposes the error-tracking configuration surface on the server SDK and adds the missing captureException overloads.

Contains two commits:

1. fix(error-tracking): pass releaseIdentifier through stateless exception capture — the stateless capture path (captureExceptionStateless, which is what posthog-server uses) never forwarded PostHogConfig.releaseIdentifier to the frame serializer, so $exception_list frames were missing map_id and could not be symbolicated. The stateful captureException path already did this; this restores parity. (Verified still missing on main as of this PR.)
2. feat(server): expose error tracking config and captureException options:
   • PostHogConfig.inAppIncludes / inAppExcludes control in_app classification of captured frames (class-name prefix match; excludes always win). inAppExcludes defaults to a new PostHogConfig.DEFAULT_IN_APP_EXCLUDES list of common JVM/framework prefixes (JDK, Kotlin, Spring, Netty, servlet containers, HTTP clients, the PostHog SDK itself) so zero-config users get a sensible your-code vs framework split. Assigning your own list replaces the defaults.
   • PostHogConfig.releaseIdentifier stamps every frame with map_id, tying events to a ProGuard/R8 mapping uploaded via posthog-cli.
   • All three are available on the config Builder.
   • New captureException(exception, distinctId, options) / captureException(exception, options) overloads take PostHogCaptureOptions with the same merging semantics as capture(..., options): custom properties, $groups, $set/$set_once, timestamp, and feature-flag enrichment via a pre-evaluated flags snapshot or appendFeatureFlags. Reserved exception properties (e.g. $exception_level, $exception_fingerprint) can be overridden through options properties. Request-context distinct-id resolution and personless fallback behave exactly like the existing overloads.

💚 How did you test it?

• 15 new tests across posthog-server's PostHogConfigTest and PostHogTest (defaults and overrides for the new config, exclude-beats-include classification, map_id stamping, and each new captureException overload including options merging and reserved-property overrides), plus 1 new core test in PostHogStatelessTest for the releaseIdentifier parity fix.
• ./gradlew :posthog:test :posthog-server:test :posthog:apiCheck :posthog-server:apiCheck pass; spotlessCheck clean. API dumps regenerated; both diffs are additive only.

📝 Checklist

• I reviewed the submitted code.
• I added tests to verify the changes.
• I updated the docs if needed.
• No breaking change or entry added to the changelog.

If releasing new changes

• Ran pnpm changeset to generate a changeset file
• Added the "release" label to the PR to indicate we're publishing new versions for the affected packages

🔗 Stacked PR

Position 2 of 4. Base: cat/java-et-coercer (PR #669).

1. PR feat(error-tracking): complete exception chain metadata and in-app classification #669 — core exception chain metadata + in-app classification
2. this PR — server error-tracking config and captureException options
3. cat/java-et-uncaught — opt-in server uncaught-exception capture
4. cat/java-et-logback — new posthog-server-logback appender module

Review after its parent; the diff shown here is only this PR's own commits once the parent merges.