Implement CLI skeleton with cobra and fx dependency injection

- Set up cobra CLI with all commands (backup, restore, prune, verify, fetch)
- Integrate uber/fx for dependency injection and lifecycle management
- Add globals package with build-time variables (Version, Commit)
- Implement config loading from YAML with validation
- Create core data models (FileInfo, ChunkInfo, BlobInfo, Snapshot)
- Add Makefile with build, test, lint, and clean targets
- Include minimal test suite for compilation verification
- Update documentation with --quick flag for verify command
- Fix markdown numbering in implementation TODO

README.md

@@ -134,7 +134,8 @@ vaultik verify <bucket> <prefix> [<snapshot_id>]
 **verify**: Validate backup integrity
 * Checks metadata hash
 * Verifies all referenced blobs exist
-* Validates chunk integrity
+* Default: Downloads blobs and validates chunk integrity
+* `--quick`: Only checks blob existence and S3 content hashes
 
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