Read preconfigured server urls

[TheOneRing]

Fixes: #261

[Copilot]

Pull Request Overview

This PR introduces a new GlobalConfig utility to read preconfigured server URLs (and other settings) from system/global policy sources, removing the old Theme-based overrides and postfix logic.

• Remove overrideServerUrl() and wizardUrlPostfix() from Theme
• Add GlobalConfig::serverUrl() and policy‐reading functions
• Update ConfigFile, wizard pages, and enums to use GlobalConfig instead of theme overrides

Reviewed Changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/libsync/theme.h / theme.cpp	Removed server‐URL override and wizard URL postfix methods
src/libsync/globalconfig.h / globalconfig.cpp	Added GlobalConfig class for system/policy config access
src/libsync/configfile.h / configfile.cpp	Refactored policy and value lookup to delegate to GlobalConfig
src/libsync/CMakeLists.txt	Added globalconfig.cpp to build
src/gui/newwizard/pages/serverurlsetupwizardpage.cpp	Switched to GlobalConfig::serverUrl() and removed theme calls
src/gui/newwizard/enums.cpp	Updated wizard state display logic to use GlobalConfig

Comments suppressed due to low confidence (1)

src/libsync/globalconfig.cpp:17

• Consider adding unit tests for GlobalConfig::getValue (and getPolicySetting on Windows) to verify correct fallback behavior across different OS paths.

QVariant GlobalConfig::getValue(QAnyStringView param, const QVariant &defaultValue)