Add GUI desktop application

- Add gui/ package: CustomTkinter app with dashboard, mods, tools, logs,
  and settings views; first-run SetupWizard for config.json generation
- Add gui.py root entry point (calls gui.run_app())
- Add selection.json for GUI selection state persistence
- Add customtkinter to requirements.txt
- Fix link_mods.py minor issues surfaced during GUI integration
- Add modlist_html/Test_Preset_A.html and Test_Preset_B.html as example inputs
- Update README.md: add GUI prerequisites, gui.py script section, gui/ folder
  structure, customtkinter to prerequisites table
- Update CLAUDE.md: add python gui.py to common commands, document GUI package
  architecture and views

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

gui/views/settings.py

@@ -0,0 +1,79 @@
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+import customtkinter as ctk
+
+from gui.views.base import BaseView
+
+if TYPE_CHECKING:
+    from gui.app import ArmaModManagerApp
+
+
+class SettingsView(BaseView):
+    """Appearance switcher, wizard re-opener, and current config display."""
+
+    def build(self) -> None:
+        self.grid_columnconfigure(0, weight=1)
+        self.grid_rowconfigure(1, weight=1)
+
+        ctk.CTkLabel(self, text="Settings",
+                     font=ctk.CTkFont(size=22, weight="bold")).grid(
+            row=0, column=0, sticky="w", padx=24, pady=(20, 8))
+
+        self._scroll = ctk.CTkScrollableFrame(self, fg_color="transparent")
+        self._scroll.grid(row=1, column=0, sticky="nsew", padx=24, pady=(0, 12))
+
+        self._build_cards()
+
+    def refresh(self) -> None:
+        # Config info may have changed (e.g. after wizard); rebuild cards.
+        for w in self._scroll.winfo_children():
+            w.destroy()
+        self._build_cards()
+
+    def _build_cards(self) -> None:
+        # ── Server & Paths ────────────────────────────────────────────────────
+        c1 = ctk.CTkFrame(self._scroll)
+        c1.pack(fill="x", pady=6)
+        ctk.CTkLabel(c1, text="Server & Path Configuration",
+                     font=ctk.CTkFont(size=14, weight="bold")).pack(
+            anchor="w", padx=16, pady=(14, 3))
+        ctk.CTkLabel(c1,
+                     text="Re-run the setup wizard to change your server URL, "
+                          "credentials, or Arma folder.",
+                     text_color="gray", wraplength=600, justify="left").pack(
+            anchor="w", padx=16, pady=(0, 8))
+        ctk.CTkButton(c1, text="Open Setup Wizard", width=160,
+                      command=self.app.open_wizard).pack(
+            anchor="e", padx=16, pady=(0, 14))
+
+        # ── Appearance ────────────────────────────────────────────────────────
+        c2 = ctk.CTkFrame(self._scroll)
+        c2.pack(fill="x", pady=6)
+        ctk.CTkLabel(c2, text="Appearance",
+                     font=ctk.CTkFont(size=14, weight="bold")).pack(
+            anchor="w", padx=16, pady=(14, 3))
+        mode_var = ctk.StringVar(value=ctk.get_appearance_mode())
+        ctk.CTkOptionMenu(c2, values=["Dark", "Light", "System"],
+                          variable=mode_var,
+                          command=ctk.set_appearance_mode,
+                          width=140).pack(anchor="w", padx=16, pady=(0, 14))
+
+        # ── Current config info ───────────────────────────────────────────────
+        cfg = self.app.cfg
+        if cfg:
+            c3 = ctk.CTkFrame(self._scroll)
+            c3.pack(fill="x", pady=6)
+            ctk.CTkLabel(c3, text="Current Configuration",
+                         font=ctk.CTkFont(size=14, weight="bold")).pack(
+                anchor="w", padx=16, pady=(14, 3))
+            info = (
+                f"Server:      {cfg.server_url}\n"
+                f"Arma dir:    {cfg.arma_dir}\n"
+                f"Downloads:   {cfg.downloads}\n"
+                f"Presets:     {cfg.modlist_html}\n"
+            )
+            ctk.CTkLabel(c3, text=info, justify="left",
+                         font=ctk.CTkFont(family="Consolas", size=11),
+                         text_color="gray").pack(anchor="w", padx=16, pady=(0, 14))