[Feature]: Don't store timestamp in the config file

[Damglador]

Feature summary

Move the timestamp from config.conf (and maybe news.json + updates.json) as well to $XDG_STATE_HOME/apdatifier or $XDG_CACHE_HOME/apdatifier, as they're not configs.

Problem / use case

I want to sync my apdatifier config between my system, because of the constantly changing timestamp, the config file is always in a changed uncommitted stated in the config repo.

Proposed solution

Move it to a separate file in the apdatifier config directory or to $XDG_STATE_HOME/apdatifier or $XDG_CACHE_HOME/apdatifier. Technically news.json and updates.json also belong there.

Alternatives considered

No response

[exequtic]

Changes made:

• You're right, updates.json and news.json are cache data, not config files. Migration to ~/.cache/apdatifier/ happens automatically on first run.
• timestamp has been removed from config.conf and KConfig. It is now stored as a single number in ~/.cache/apdatifier/lastCheck.
• Paths now follow the XDG Specification with $APDATIFIER_CONFIG_DIR and $APDATIFIER_CACHE_DIR as the first priority.

Resolution order: $APDATIFIER_CONFIG_DIR → $XDG_CONFIG_HOME → ~/.config (same for cache).