Fix bspwm black screen: add provision() delegation and default configs

[Softer]

bspwm profile installs packages but does not provision configuration files. After login via lightdm the user sees a black screen with no keybindings because ~/.config/bspwm/bspwmrc and ~/.config/sxhkd/sxhkdrc do not exist.

Two fixes:

• DesktopProfile did not override provision() to delegate to sub-profiles (unlike ServerProfile), so BspwmProfile.provision() was never called. Added the missing delegation.
• BspwmProfile.provision() now copies example configs from /usr/share/doc/bspwm/examples/ to each user's ~/.config/ and makes bspwmrc executable. This matches what the Arch Wiki recommends for a minimal working setup.

[svartkanin]

Why are they behind a type check?

[Softer]

As far as I understand - python 3.14 evaluates annotations lazily (PEP 649), so Installer and User are never resolved at runtime - they're only used by type checkers. TYPE_CHECKING avoids importing heavy modules (Installer pulls in a lot) and sidesteps potential circular imports.

[svartkanin]

Are there actual circular deps? If not we shouls define these as regular imports

[Softer]

Yes, there are no cyclic dependencies right now. I didn't want to have them in the future. But you're right, it's probably overengineering.

[svartkanin]

Sometimes it's good to encounter them as that means the code not well structured and probably needs refactoring