v1.9.1: PNG Material Design icons — 28 icons, dark/light theme, HiDPI, graceful Unicode fallback

- 56 PNG icons (28 unique × 2 color variants) from Material Design Icons (round style, 96×96px)
- core/icons.py: ctk_icon(), make_icon_button(), reconfigure_icon_button() with CTkImage cache
- Updated 15 GUI files: app.py, sidebar.py, server_dialog.py, all tabs
- build.py: auto-include assets/icons/ in PyInstaller bundle, patch rollover at 99→minor+1
- tools/download_icons.py: icon download script
- Automatic dark↔light theme switching via CTkImage dual-image support

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

gui/tabs/info_tab.py

@@ -4,7 +4,7 @@ Info tab — display server details, edit button.
 
 import customtkinter as ctk
 from core.i18n import t
-from core.icons import icon_text
+from core.icons import icon_text, make_icon_button
 
 
 class InfoTab(ctk.CTkFrame):
@@ -56,7 +56,7 @@ class InfoTab(ctk.CTkFrame):
             self._fields[key] = val
 
         # Edit button
-        self.edit_btn = ctk.CTkButton(self, text=icon_text("edit", t("edit_server_btn")), command=self._on_edit)
+        self.edit_btn = make_icon_button(self, "edit", t("edit_server_btn"), command=self._on_edit)
         self.edit_btn.pack(pady=15)
 
     def set_server(self, alias: str | None):