style: move widget colors to the shared palette

Same mechanical swap for the widgets and the tutorial manager: painter
QColors go through qcolor(), inline QSS literals become palette
constants (baton dialog, busy overlay, status bar, camera overlays,
splash screen, numeric inputs).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/aare/gui/tutorials/tutorial_manager.py

@@ -15,10 +15,19 @@ from PySide6.QtCore import (
     QTimer,
     Signal,
 )
-from PySide6.QtGui import QColor, QPainter, QPen
+from PySide6.QtGui import QPainter, QPen
 from PySide6.QtWidgets import QLabel, QPushButton, QWidget
 
 from aare.gui.constants import LOGGER_NAME
+from aare.gui.styles import (
+    DEFAULT_TEXT,
+    NOTE_TEXT,
+    SHADOW,
+    TUTORIAL_BORDER,
+    TUTORIAL_HIGHLIGHT,
+    WHITE,
+    qcolor,
+)
 from aare.gui.tutorials.tutorial_models import (
     StepFlow,
     StepStatus,
@@ -95,11 +104,11 @@ class TutorialOverlay(QWidget):
         self.anim.valueChanged.connect(self.update)
 
         self.callout = QLabel(self)
-        self.callout.setStyleSheet("""
-            background: white;
-            color: black;
+        self.callout.setStyleSheet(f"""
+            background: {WHITE};
+            color: {DEFAULT_TEXT};
             padding: 16px;
-            border: 2px solid #555;
+            border: 2px solid {TUTORIAL_BORDER};
             border-radius: 10px;
             font-size: 16px;
         """)
@@ -185,10 +194,10 @@ class TutorialOverlay(QWidget):
 
     def paintEvent(self, event) -> None:
         painter = QPainter(self)
-        painter.fillRect(self.rect(), QColor(0, 0, 0, int(150 * self.opacity)))
+        painter.fillRect(self.rect(), qcolor(SHADOW, int(150 * self.opacity)))
 
         if self.current_rect.isValid():
-            pen = QPen(Qt.yellow, 4)
+            pen = QPen(qcolor(TUTORIAL_HIGHLIGHT), 4)
             painter.setPen(pen)
             painter.setBrush(Qt.NoBrush)
             painter.drawRoundedRect(self.current_rect, 8, 8)
@@ -219,7 +228,7 @@ class TutorialOverlay(QWidget):
         if view.body.strip():
             text_parts.append(view.body)
         if view.hint:
-            text_parts.append(f"<span style='color:#555;'><i>{view.hint}</i></span>")
+            text_parts.append(f"<span style='color:{NOTE_TEXT};'><i>{view.hint}</i></span>")
 
         self.callout.setText("<br><br>".join(text_parts))
         self.callout.setMaximumWidth(460)