feat: Implement initial Sprite Editor application with basic UI components

- Added main application class `SpriteEditorApp` with layout setup.
- Created menu bar with placeholder options.
- Implemented `BottomToolbarView`, `LeftSidebarView`, `MainEditorView`, `RightSidebarView` with basic UI elements.
- Added dialog classes for `ExportSettingsDialog` and `FlipbookCreatorDialog` to manage export settings and flipbook creation.
- Introduced support for loading and displaying images in the flipbook creator.
- Established a structure for handling sprite sheet composition and preview rendering.

views/main_editor.py

@@ -0,0 +1,20 @@
+import tkinter as tk
+from tkinter import ttk
+
+
+class MainEditorView(ttk.LabelFrame):
+    def __init__(self, parent) -> None:
+        super().__init__(parent, text="Main Editor (Placeholder)")
+        self.columnconfigure(0, weight=1)
+        self.rowconfigure(0, weight=1)
+
+        canvas = tk.Canvas(self, bg="#2c2c2c", highlightthickness=0)
+        canvas.grid(row=0, column=0, sticky="nsew", padx=8, pady=8)
+        canvas.create_text(
+            220,
+            160,
+            text="Sprite Editing Area Placeholder",
+            fill="#f0f0f0",
+            font=("Segoe UI", 12),
+        )
+