Polish settings, add matching defaults, drop pkg2zip, externalize infra config

- Rework Settings tab into grouped sections
- Add preferred-region matching and full-hash-by-default setting
- Replace combo-box square arrow with a proper chevron
- Fix UMD Refresh button (clicked bool was clearing the view)
- Remove pkg2zip.exe fallback (pure-Python decryptor is the primary path)
- Move LAN IP/share paths to .env; use example defaults in config

app/style.py

@@ -7,6 +7,8 @@ single cohesive dark theme here makes the whole UI consistent.
 """
 from PySide6.QtGui import QColor, QPalette
 
+from . import config
+
 # Design tokens
 BG = "#1e1f24"        # window background
 SURFACE = "#26272e"   # cards, inputs, table headers
@@ -19,6 +21,7 @@ TEXT_FAINT = "#6f7079"
 ACCENT = "#4a9eff"
 ACCENT_HOVER = "#6bb0ff"
 
+
 _STYLESHEET = f"""
 QMainWindow {{
     background: {BG};
@@ -105,10 +108,9 @@ QComboBox::drop-down {{
     width: 22px;
 }}
 QComboBox::down-arrow {{
-    image: none;
-    border-left: 4px solid transparent;
-    border-right: 4px solid transparent;
-    border-top: 5px solid {TEXT_DIM};
+    image: url(__CHEVRON__);
+    width: 12px;
+    height: 8px;
     margin-right: 6px;
 }}
 QComboBox QAbstractItemView {{
@@ -310,4 +312,5 @@ def apply_theme(app):
     """Apply the dark Fusion theme to ``app`` (call once before showing UI)."""
     app.setStyle("Fusion")
     app.setPalette(_dark_palette())
-    app.setStyleSheet(_STYLESHEET)
+    chevron = str(config.resource_path("img", "chevron.png"))
+    app.setStyleSheet(_STYLESHEET.replace("__CHEVRON__", chevron))