Use /opt for Debian package app files (also RPM and Pacman)

[yamixst]

This PR changes the default installation directory for .deb packages from /usr/share/{binary_name} to /opt/{binary_name}.

Motivation

According to the Filesystem Hierarchy Standard (FHS), /usr/share is intended for architecture-independent, read-only data — things like documentation, icons, locale files, and .desktop entries. It is not meant to hold application binaries or their runtime dependencies.

/opt, on the other hand, is specifically designated for self-contained, add-on application software packages. Each application gets its own subtree (/opt/{package}), where it can place binaries, libraries, and any other files it needs — without mixing them into the shared system directories.

Why this matters

	/usr/share/{name}	/opt/{name}
FHS purpose	Static, arch-independent data	Self-contained third-party apps
Placing binaries here	Violates FHS	Correct per FHS
Isolation	Files mix with system packages	Clean per-app directory
Uninstall cleanliness	Scattered files harder to track	Single directory to remove
Lintian / rpmlint	May produce warnings	No warnings

Packaging tools like lintian flag binaries placed under /usr/share as a policy violation. Moving to /opt resolves this and aligns with how other third-party .deb distributors (Chrome, VS Code, Discord, Zoom, etc.) package their applications.