Pin client chart's ingestor digest to v0.3.1

[saadqbal]

Context

tracebloc/data-ingestors v0.3.1 released today (release notes, tracked in data-ingestors#120) carrying two real bug fixes:

• data-ingestors#108 — copy tokenizer.json to training pod for MLM datasets. Without it the client fell back to bert-base-uncased (vocab=30522), exceeding user models' nn.Embedding and crashing training with a CUDA device-side assert.
• data-ingestors#119 — close YAML-vs-template parity gaps in per-category metadata (tabular number_of_columns, keypoint target_size / number_of_keypoints, tabular na_values).

The chart's images.ingestor.digest in client/values.yaml is still pinned to v0.3.0's sha (sha256:463e236748708a5e3564569eec9173ea8cb3bcf515992d4939c5b610f3807a4a). Per the comment block on that field, the pin is the baseline digest for greenfield installs — ongoing clusters get the upgrade via the image-refresh CronJob, but new deployments and the chart-stamped fallback need explicit bumps.

New digest: sha256:a0861ea9fbf4653279351ee30af9ebe2b75fcacd391923b681631312f4a85ee4.

Scope

• client/values.yaml — update images.ingestor.digest to the v0.3.1 sha and refresh the explanatory comment to reference the v0.3.1 fixes.
• client/Chart.yaml — bump version 1.4.0 → 1.4.1 (and appVersion).

Out of scope

• feat(#158): auto-refresh ingestor image digest without chart release #159 (image-refresh for ingestor) will obsolete this manual-pin pattern as soon as it lands. This ticket and PR exist because feat(#158): auto-refresh ingestor image digest without chart release #159 needs a dev-cluster smoke test before it can merge, and the v0.3.1 fixes have real customer impact (MLM training crash). Manual pin now; feat(#158): auto-refresh ingestor image digest without chart release #159 makes future pins automatic.
• The author of feat(#158): auto-refresh ingestor image digest without chart release #159 will need to rebase from 1.4.1 (this PR's bump) to 1.4.2 after this lands. Sequencing nuisance, not a blocker.

[saadqbal]

Pin landed in #161 (merged into develop at 4249046). v0.3.1 digest now the chart's baseline; #159 will obsolete this manual-pin pattern once it lands.