feat: Add customizable accent color setting

Introduce an accent color preference across the app: add a settings UI input (with restart note), persist it to AppState and config (read/write), and accept it in save_settings. Integrate the value into theming: compute a semi-transparent selection color, apply it to table selection styles, and pass it to qdarktheme as the primary color (including when window transparency is enabled). Also apply the accent to the tracker combo selection styling as a UI polish.

src/interface/dialogs/theme.py

@@ -1,4 +1,6 @@
 from PySide6.QtGui import QColor
+from utils.logging.logs import consoleLog
+from utils.data.state import state
 import darkdetect
 
 def _is_dark_mode():
@@ -27,15 +29,32 @@ def _theme_colors():
         }
 
 
+def _accent_selection_color(alpha: float = 0.35) -> str:
+    if not state.accent_color:
+        return None
+    try:
+        hex_color = state.accent_color.lstrip('#')
+        if len(hex_color) != 6:
+            return None
+        r, g, b = int(hex_color[0:2], 16), int(hex_color[2:4], 16), int(hex_color[4:6], 16)
+        return f"rgba({r}, {g}, {b}, {alpha})"
+    except ValueError:
+        consoleLog(f"Invalid Color: {state.accent_color}")
+        return None
+
+
 def _table_stylesheet(view_type="QTableWidget"):
     c = _theme_colors()
     dark = _is_dark_mode()
     color_rule = "" if dark else f"color: {c['text']};"
+    selected_bg = _accent_selection_color() or c["selected"]
+    selection_color_rule = f"selection-background-color: {selected_bg};" if state.accent_color else ""
     return f"""
         {view_type} {{
             border: none;
             outline: 0;
             font-size: 13px;
+            {selection_color_rule}
             {color_rule}
         }}
         {view_type}::item {{
@@ -45,7 +64,7 @@ def _table_stylesheet(view_type="QTableWidget"):
             {color_rule}
         }}
         {view_type}::item:selected {{
-            background: {c["selected"]};
+            background: {selected_bg};
             outline: none;
             border: none;
             border-bottom: 1px solid {c["border"]};