feat: per-job log sink for ProgressDisplay

[Sootopolis]

Summary

• Introduces JobLogSink (trait + StdoutSink default + currentSink: FiberRef[JobLogSink]) in ccas.utils. ProgressDisplay.asZLogger resolves the active sink from the ZLogger callback's context map so the lookup stays sync while inheriting across forked children.
• Adds FileSink in ccas.server.jobs — per-job, appends ANSI-stripped lines to ${job-logs.directory}/<jobId>.log, tees raw to stdout. JobRunner.submit wraps each runJob in JobLogSink.currentSink.locally(FileSink(...)) so success/failure handlers' logs also land in the file.
• JobLogTransport trait stub added; FileTail impl deferred to File-tail logs endpoint GET /api/jobs/{id}/logs #47.
• HOCON: job-logs.directory = "logs/jobs" (prod, env override JOB_LOGS_DIR) and target/test-job-logs (test). Directory created once at JobRunner.live startup.

Closes #42. Unblocks #47.

Test plan

• sbt compile clean (only intentional : Unit annotation, no warnings).
• New TestJobLogSink (5 tests): default sink identity, file-append, ANSI-strip, stdout-tee, currentSink.locally routing through ProgressDisplay.live.
• New testSubmitWritesJobLog in TestJobRunner: end-to-end job → log file contains the message, no ESC bytes.
• TestProgressBar regression — all 13 existing assertions pass (default StdoutSink preserves current behaviour byte-for-byte).
• Full sbt test — 736 pass.

Follow-ups

• FileSink: revisit sustained write-failure handling #52 — Revisit FileSink behaviour under sustained write failures (stderr-spam latch trade-off).
• FileSink: hold per-job writer open, drop file IO out of ProgressDisplay lock #53 — Hold per-job BufferedWriter open; move file IO out of ProgressDisplay's lock (bundle with File-tail logs endpoint GET /api/jobs/{id}/logs #47 lifecycle work).

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