fix(gui): make dialogs readable (dark theme)

The update prompt and changelog dialogs inherited the app's light text color on a
default light Fusion background, making them unreadable. Style QDialog/QMessageBox
with the dark theme and readable text.

src/rigdoctor/__init__.py

@@ -1,3 +1,3 @@
 """RigDoctor — modular hardware monitoring & crash diagnostics for Linux gamers."""
 
-__version__ = "0.1.0"
+__version__ = "0.1.1"

src/rigdoctor/gui/theme.py

@@ -119,4 +119,9 @@ QPushButton#LinkButton {{
     text-align: left; padding: 0; text-decoration: underline;
 }}
 QPushButton#LinkButton:hover {{ color: {TEXT}; }}
+
+/* Dialogs (update prompt, changelog) — match the dark theme so text is readable. */
+QDialog {{ background: {BG}; }}
+QMessageBox {{ background: {CARD}; }}
+QDialog QLabel, QMessageBox QLabel {{ color: {TEXT}; background: transparent; }}
 """