Task: Make ImageCache batching byte-size aware, add SVG compression

First, weigh the three options the parent story lays out: (a) byte- size-aware NATS batching, (b) add compression to the existing NATS request-reply path, (c) move image transfer to the existing S3-like HTTP storage endpoint (GET /api/v1/storage/{bucket}/{key}, ores.http.core/routes/storage_routes.hpp) the way ores.compute.wrapper already downloads binaries. These aren't mutually exclusive (HTTP transfer would still benefit from compression), but the batching-vs-transport question should be decided explicitly before implementing, not defaulted to "patch what's there." Then implement the chosen approach so that country flags (and any other batch-loaded image set) never partially fail to load again, regardless of how many or how large the images in a given request are.

• A written decision (recorded in this task's * Plan, distilled to the story's * Decisions at close) on NATS-byte-aware-batching vs. HTTP storage-endpoint transfer vs. both, with rationale.
• No image batch (however constructed) can silently fail to load due to exceeding a transport payload limit – verified against a synthetic worst case of many large SVGs requested together.
• Image data is compressed on the wire regardless of which transport is chosen.
• MAX_IMAGES_PER_REQUEST (currently lowered to 15 as an interim mitigation) is revisited once the real fix lands – raised back up, removed, or reinterpreted depending on the chosen transport.

(Implementation strategy. Written when work starts; key decisions are distilled into the parent story's * Decisions at close, but the plan itself stays — it is the historical record of what we did.)

This task bundled a design decision (batching vs. compression vs. HTTP transport) with two independent implementation concerns (byte-aware batching, compression) under one heading. Split on 2026-07-26 into:

• Decide: NATS binary+compression vs. HTTP storage-endpoint transport for image delivery
• Add gzip compression to the image NATS pipeline, send raw bytes instead of base64
• Make ImageCache batching byte-size aware

Manual QA scenarios (scaffolded via compass add test_scenario, run through the QA Validation Runner panel) that verify this task. Link new ones here as they're created; the scenario doc itself links back via its "Verifies task" field.