PC Explorer visualization (damage classification COG) - #175

Stacked feature (-pc-explorer): make PC published collections explorable
by rendering a licensing-safe damage classification COG (our derived
output, no source pixels) plus the render-option/mosaic/tile-settings
configuration the Explorer requires.

Expose the Explorer-render toggle as a first-class deploy input across
both paths (functions.bicep + main.bicep/param, deploy_apps.sh, and the
deploy-apps workflow), mirroring PC_PROVIDER_ENABLED. Defaults on. The
advanced raster knobs stay code-defaults (rarely tuned). Env-drift check
green; bicep builds.

- raster/provider: only produce the damage_class COG when a predicted-damage
  geopackage is present. A footprints-only publish has no damage column, so
  rasterizing it would publish a misleading all-undamaged layer -- skip both
  the rasterize and the reuse-of-staged-COG paths.
- finalize_unpublish: always delete the dataset-specific published/<id>/ prefix
  instead of gating on the current feature flags. If rendering was enabled at
  publish and disabled before unpublish, the staged COG would otherwise leak.
- transport: accept HTTP 409 as idempotent success when creating render options
  and mosaics, so a concurrent publish racing the get-then-create doesn't abort
  before mosaic/tile-settings are registered.
- config: add _get_bounded_float_env and bound PUBLISH_DAMAGE_RASTER_METERS to a
  positive finite float, so an operator typo fails fast with a clear message
  rather than crashing provider construction or raster generation.
- tests: assert the COG's projected CRS, resolution, and AOI-derived bounds;
  cover the footprints-only skip, the always-clean unpublish, and 409 tolerance.
- spec: add a Contents list to explorer-visualization.md.

- raster: replace the sorted(zip(...)) with an explicit two-pass partition
  (undamaged then damaged). O(n) instead of O(n log n), no intermediate
  sorted copy, and avoids relying on a sort key to keep non-orderable
  shapely geometries from being compared. damaged_count now counts the
  geometries actually burned (skips empty ones). (mgmachado)
- provider: soften the _stage_damage_class_asset docstring so the
  best-effort guarantee isn't read as unconditional -- an OOM-kill
  terminates the worker rather than raising, so it can still fail the
  publish; the per-side pixel cap keeps that path unlikely. (mgmachado)
- spec: add a Resource use section documenting the raster memory bound
  (~400 MB at the 20000-px ceiling vs a 4096 MB instance) and that
  vector-side memory is uncapped and scales with building count. (mgmachado)
- deploy_apps.sh: drop the lone inline comment on the publishing env block
  to match the surrounding params. (calebrob6)