Rparadox 0.1.5

CRAN check Note fix

Added a high-level read_paradox() function for a simple, one-step workflow to read Paradox files. This is now the recommended function for most users.
Added a pxlib_metadata() function to retrieve database metadata (number of records, field details, encoding) without reading the entire dataset.

The architecture for handling character encodings has been completely refactored. The C-level code now returns raw character data, and all conversion to UTF-8 is handled reliably in R via the stringi package(ICU) instead of Riconv. This fixes test failures on CRAN and improves robustness for files on various operating systems.
Added stringi to package imports.
Added extensive tests for the new read_paradox() and pxlib_metadata() functions.
Documentation and examples have been updated to reflect the new functions and recommended workflow.

Fixed CRAN check issues on Debian: package no longer attempts to open Paradox files in write mode (rb+ → rb). This ensures full compliance with CRAN Policy (no writes outside of temporary directories).
Fixed heap-buffer-overflow in PX_get_data_alpha (discovered with AddressSanitizer). Now the function safely respects field length and prevents out-of-bounds reads for fixed-length strings without \0.
Improved handling of invalid/null Paradox dates with an upper bound filter for extreme values.
Added proper .gitignore entries for cran-comments.md and CRAN-SUBMISSION.
Updated README with CRAN badges and installation instructions.
Expanded test coverage: re-enabled datasets with German, English and Russian encodings, including CP866.

Fixed CRAN feedback:
- Removed unnecessary \dontrun{} in examples.
  Added fast, self-contained examples using demo files
  (biolife.db, of_cp866.db in inst/extdata).
- Ensured no commented-out example code remains.
- All examples now run in < 5s and without commented-out code.
Fixed vignette build issue on CRAN check servers:
- Explicitly added rmarkdown in VignetteBuilder
  to avoid failures when running with --no-suggests.
Memory management improvements:
- Fixed memory leaks in src/interface.c when reading BLOB fields.
- Examples and vignette now run cleanly under Valgrind.
Verified that all examples run in < 5 sec and vignettes build
successfully across test environments.