feat(image): add property support to create/update/show

[kallioli]

Context

The CLI could not set or update custom Glance image properties
(os_distro, os_version, hw_qemu_guest_agent,
cinder_img_volume_type, …), which made inter-cloud image migration
lossy: properties present on the source image were silently
dropped on re-upload. This PR is the building block needed for a
future orca image migrate (out of scope here, tracked separately).

Changes

• orca image create --property KEY=VALUE (repeatable). Properties
  ride on the Glance v2 POST body as top-level keys.
• orca image update --property KEY=VALUE and --remove-property KEY
  compose into a single atomic JSON-Patch document. Add-vs-replace
  is decided after fetching the current image so untouched properties
  survive. Removes are strict by default and turn idempotent under
  --ignore-missing.
• orca image show surfaces every custom property Glance returns
  plus integrity fields (checksum, os_hash_algo, os_hash_value,
  direct_url, tags):
  • table: a Properties sub-table after the standard fields,
    sorted by key
  • json: a top-level "properties" aggregate; each custom key
    is also mirrored at the JSON root for backward compatibility
    (jq .os_distro keeps working alongside jq .properties.os_distro)
  • value: trailing KEY VALUE lines after the standard fields

Property keys are validated client-side against Glance's
^[A-Za-z0-9_:.\-]{1,255}$ schema before any HTTP round-trip —
malformed keys fail fast with a friendly error instead of an opaque
Glance 400. Only the first = splits a value, so URL-like values
(--property url=https://x?a=1&b=2) survive intact.

Tests

15 new tests under tests/test_image.py covering the full lifecycle:

• create round-trip with multiple --property flags
• create rejects bad keys before any HTTP write
• create accepts values containing =
• update emits replace for existing keys, add for new ones
• update mixes --property and --remove-property in one patch
• update remove is strict by default, idempotent under --ignore-missing
• show renders the Properties sub-table (table format)
• show nests properties under a top-level properties key (json)
• show dual-renders custom props at the JSON root (rétrocompat)
• show emits KEY VALUE lines (value format)
• show omits the sub-table when there are no custom properties

pytest -q --cov=orca_cli --cov-fail-under=85: 2338 passed, coverage
88.42%. ruff + mypy clean.

Risks

• os_distro and os_version move from the standard image show
  field set into the Properties section. Table/value users see them
  in a different visual section. JSON consumers are unaffected
  thanks to the dual-render at the root. Documented in CHANGELOG.
• No new dependencies. Reuses the existing JSON-Patch path on
  ImageService.update. Service layer untouched.

Out of scope (tracked separately)

• One-shot orca image migrate (cloud-to-cloud copy preserving
  everything). This PR is the building block it needs.
• Property deletion on image create (no use case yet).
• Schema-aware completion of well-known property keys (nice-to-have).