refactor: extract volume and image matching logic from rm_build.rs

[mukeshblackhat]

Summary

• Extracted two pure matching functions from async Docker-dependent code in coast-daemon/src/handlers/rm_build.rs:
  • volume_belongs_to_project(name, project, labels) — checks shared, compose, shared-services, and isolated volume naming patterns with label verification
  • image_matches_project(repo_tags, project) — checks repo tags for coast-image/{project}: and {project}-coasts prefixes
• Updated remove_project_volumes and remove_project_images to delegate to the new helpers
• Added 13 unit tests covering all matching cases
• Existing #[allow(clippy::...)] annotations on the handle functions are kept as-is per ticket scope

What was there before

remove_project_volumes and remove_project_images had matching logic inlined inside async Docker-dependent loops. This made it impossible to unit test the matching rules without a real Docker daemon.

What changed

Single file: coast-daemon/src/handlers/rm_build.rs

Extracted functions (both private, pure, no async):

Function	What it checks
volume_belongs_to_project	Shared volumes (coast-shared--{project}--), compose volumes ({project}-coasts), shared-services volumes ({project}-shared-services), isolated volumes (coast-- + label match)
image_matches_project	Tags starting with coast-image/{project}: or {project}-coasts

Parent functions updated:

• remove_project_volumes — replaced inline matching with volume_belongs_to_project call
• remove_project_images — replaced inline matching with image_matches_project call

13 unit tests added:

volume_belongs_to_project (8 tests):

• Shared volume matches / different project doesn't
• Compose volume matches
• Shared-services volume matches
• Isolated volume with correct label / wrong label / no label
• Unrelated volume doesn't match

image_matches_project (5 tests):

• Coast image tag matches
• Coasts compose image matches
• Different project doesn't match
• Empty tags doesn't match
• Multiple tags, one matches

Test plan

Verify the extraction

# Run only the new tests
cargo test -p coast-daemon -- rm_build::tests

# Should see 13 tests pass

Run lint and full tests

# Zero warnings expected
make lint

# All tests pass
make test

Verify behavior is unchanged

# The matching logic is pure — same rules as before:
# - coast rm-build still removes the correct volumes and images
# - No Docker behavior changed, just code organization

Closes #121

[jamiesunderland]

Perfect! Thanks @mukeshblackhat