Remove numlockx dependency

[atharvafulay]

Summary

• remove the X11-only numlockx startup invocation
• remove the now-unused activate_numlock setting
• remove the obsolete sample configuration key
• leave the Num Lock state indicator unchanged

Why

numlockx only operates on X11. Keeping the external process invocation in the greeter leaves a dead and misleading configuration path as the project moves through its Wayland-capable startup flow. Removing the complete integration fixes the dependency at its source instead of suppressing spawn errors.

Fixes #898.

Validation

• git diff --check
• verified there are no remaining numlockx, activate_numlock, or activate-numlock references under src/ or data/
• meson setup build reached dependency resolution, then stopped because Homebrew does not provide a supported wayland-scanner bottle on this macOS host; the Linux CI build is required for full compilation

AI disclosure

OpenAI Codex assisted with repository research, the focused edit, and validation. I reviewed the final diff before publishing.

[danirabbit]

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