Make the lock-screen wallpaper blur configurable

[wbuf81]

What would you like?

Please make the wallpaper blur on the Quickshell lock screen configurable through the Omarchy
shell theme/config.

The lock screen already uses the currently selected theme wallpaper, which looks great. However,
shell/plugins/lock/LockView.qml currently applies the strongest blur whenever the wallpaper is
loaded.

A numeric theme value would let users choose between a crisp wallpaper and the current full blur:

[lock]
blur-strength = 0.0

A value of 0.0 would disable the blur, while 1.0 would preserve the current default. Values
between them would allow themes and users to choose a softer effect.

Why would this be useful?

Some theme wallpapers are designed to remain attractive and readable behind the centered password
field. The current full blur hides much of their artwork.

The only available workaround is cloning the entire omarchy.lock plugin and changing one QML
line. Because that clone also contains the session-lock and PAM integration, it no longer
automatically receives future upstream lock-screen fixes. That is a large maintenance and security
tradeoff for a purely visual preference.

Suggested behavior

• Preserve the existing full blur as the default.
• Accept a blur strength between 0.0 and 1.0.
• Treat 0.0 as no blur and avoid running the blur effect unnecessarily.
• Allow the setting to come from a theme or user shell configuration.
• Continue using the active wallpaper and existing contrast treatment.
• Avoid requiring users to clone the security-sensitive lock service.

Related discussion

Discussion #9076 identifies the same underlying problem for display blanking: small lock-screen
preferences currently require cloning the entire security-sensitive lock plugin. This request is
specifically about making the wallpaper blur configurable.

#9076