feat(core): add OpenCV-style logging facade (#80)

[kalwalt]

Summary

Add a new core::logging module mirroring OpenCV's cv::utils::logging, built on the existing log crate facade.

Closes #80

What's included

LogLevel enum

7 variants: Silent, Fatal, Error, Warning, Info, Debug, Verbose with bidirectional conversions to/from log::LevelFilter and log::Level.

Functions

• set_log_level(LogLevel) -> LogLevel — returns previous level (OpenCV semantics)
• get_log_level() -> LogLevel

tags submodule

Per-subsystem constants: PURECV, CORE, IMGPROC, FEATURES2D, CALIB3D, VIDEO

Macros (all #[macro_export])

Family	Macros
Level	cv_log_fatal!, cv_log_error!, cv_log_warning!, cv_log_info!, cv_log_debug!, cv_log_verbose!
Once-per-site	cv_log_once_error!, cv_log_once_warning!, cv_log_once_info!, cv_log_once_debug!
Conditional	cv_log_if_error!, cv_log_if_warning!, cv_log_if_info!, cv_log_if_debug!

Example usage

use purecv::core::logging::{self, tags, LogLevel};

logging::set_log_level(LogLevel::Info);
purecv::cv_log_info!(tags::IMGPROC, "gaussian blur, ksize = {}", 5);
purecv::cv_log_if_warning!(tags::CORE, ksize % 2 == 0, "even kernel size: {}", ksize);

Files changed (6)

File	Change
src/core/logging.rs	NEW — main module
src/core.rs	Register module, add re-exports
src/core/utils.rs	Remove old log functions, add re-exports from logging
src/lib.rs	Add LogLevel + tags to prelude
src/version.rs	Migrate log::info! to cv_log_info!
src/core/tests.rs	Add 10 logging tests

Breaking change

set_log_level / get_log_level now take/return LogLevel instead of log::LevelFilter. These functions had zero callers in the entire codebase and the crate is pre-1.0 (0.6.1).

Verification

• cargo fmt -- --check (clean)
• cargo clippy -- -D warnings (0 warnings)
• cargo test (305 unit tests + 39 doc-tests passed)