Add regex filtering support (Fixes #554)

[sabbellasri]

Added --text, --regex, --smart
Regex filtering path in View::filter
Interactive regex edit in watch mode (/, Enter, Esc)
regex moved to top-level dependencies for cross-platform build compatibility.

[sabbellasri]

Hi @dalance Following are the changes

Added new CLI search mode flags in opt.rs: --text, --regex, and --smart (mutually exclusive).

Kept existing text/numeric search logic unchanged, and added a separate regex path in view.rs so regex is only used when regex mode is active.

Added smart regex detection in util.rs (has_regex_syntax) to auto-switch behavior in --smart mode when regex-like symbols are present.

Added argument validation in main.rs:

--regex accepts only one pattern argument.
--smart also enforces single-pattern usage when regex syntax is detected.
Added interactive regex editing in watch mode in watcher.rs: press / to edit filter, Enter to apply, Esc to cancel, backspace support, and regex error display in header.

Updated dependency placement in Cargo.toml: moved regex to top-level [dependencies] so builds work on macOS/Linux/Windows (not only Linux/Android).

The CI checks appear to be waiting for workflow approval.
Could a maintainer please approve the workflow so the builds can run?

Thank you!