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/dialogs/export_settings_dialog.py

@@ -0,0 +1,120 @@
+from dataclasses import dataclass
+import tkinter as tk
+from tkinter import ttk, messagebox
+
+
+@dataclass
+class ExportSettings:
+    orientation: str = "horizontal"
+    spacing: int = 0
+    margin: int = 0
+    rows: int = 0
+    columns: int = 0
+    output_name: str = "flipbook.png"
+
+
+class ExportSettingsDialog(tk.Toplevel):
+    def __init__(self, parent: tk.Misc, initial_settings: ExportSettings | None = None) -> None:
+        super().__init__(parent)
+        self.title("Default Export Settings")
+        self.resizable(False, False)
+        self.transient(parent)
+        self.grab_set()
+        self.result: ExportSettings | None = None
+
+        settings = initial_settings or ExportSettings()
+        self.orientation_var = tk.StringVar(value=settings.orientation)
+        self.spacing_var = tk.StringVar(value=str(settings.spacing))
+        self.margin_var = tk.StringVar(value=str(settings.margin))
+        self.rows_var = tk.StringVar(value=str(settings.rows))
+        self.columns_var = tk.StringVar(value=str(settings.columns))
+        self.output_name_var = tk.StringVar(value=settings.output_name)
+
+        container = ttk.Frame(self, padding=10)
+        container.grid(row=0, column=0, sticky="nsew")
+        container.columnconfigure(1, weight=1)
+
+        ttk.Label(container, text="Orientation").grid(row=0, column=0, sticky="w", pady=4)
+        orientation_combo = ttk.Combobox(
+            container,
+            state="readonly",
+            values=["horizontal", "vertical"],
+            textvariable=self.orientation_var,
+            width=20,
+        )
+        orientation_combo.grid(row=0, column=1, sticky="ew", pady=4)
+
+        ttk.Label(container, text="Frame Spacing (px)").grid(row=1, column=0, sticky="w", pady=4)
+        ttk.Spinbox(container, from_=0, to=999, textvariable=self.spacing_var, width=10).grid(
+            row=1, column=1, sticky="w", pady=4
+        )
+
+        ttk.Label(container, text="Margin (px)").grid(row=2, column=0, sticky="w", pady=4)
+        ttk.Spinbox(container, from_=0, to=999, textvariable=self.margin_var, width=10).grid(
+            row=2, column=1, sticky="w", pady=4
+        )
+
+        ttk.Label(container, text="Rows (0 = auto)").grid(row=3, column=0, sticky="w", pady=4)
+        ttk.Spinbox(container, from_=0, to=999, textvariable=self.rows_var, width=10).grid(
+            row=3, column=1, sticky="w", pady=4
+        )
+
+        ttk.Label(container, text="Columns (0 = auto)").grid(row=4, column=0, sticky="w", pady=4)
+        ttk.Spinbox(container, from_=0, to=999, textvariable=self.columns_var, width=10).grid(
+            row=4, column=1, sticky="w", pady=4
+        )
+
+        ttk.Label(container, text="Default File Name").grid(row=5, column=0, sticky="w", pady=4)
+        ttk.Entry(container, textvariable=self.output_name_var, width=24).grid(row=5, column=1, sticky="ew", pady=4)
+
+        actions = ttk.Frame(container)
+        actions.grid(row=6, column=0, columnspan=2, sticky="e", pady=(10, 0))
+        ttk.Button(actions, text="Cancel", command=self._cancel).grid(row=0, column=0, padx=4)
+        ttk.Button(actions, text="Apply", command=self._apply).grid(row=0, column=1, padx=4)
+
+        self.protocol("WM_DELETE_WINDOW", self._cancel)
+
+    def show(self) -> ExportSettings | None:
+        self.wait_window(self)
+        return self.result
+
+    def _apply(self) -> None:
+        try:
+            spacing = int(self.spacing_var.get())
+            margin = int(self.margin_var.get())
+            rows = int(self.rows_var.get())
+            columns = int(self.columns_var.get())
+        except ValueError:
+            messagebox.showerror(
+                "Invalid settings",
+                "Spacing, margin, rows, and columns must be valid whole numbers.",
+                parent=self,
+            )
+            return
+
+        if spacing < 0 or margin < 0 or rows < 0 or columns < 0:
+            messagebox.showerror("Invalid settings", "Spacing, margin, rows, and columns cannot be negative.", parent=self)
+            return
+
+        orientation = self.orientation_var.get()
+        if orientation not in {"horizontal", "vertical"}:
+            messagebox.showerror("Invalid settings", "Orientation must be horizontal or vertical.", parent=self)
+            return
+
+        output_name = self.output_name_var.get().strip() or "flipbook.png"
+        if not output_name.lower().endswith(".png"):
+            output_name = f"{output_name}.png"
+
+        self.result = ExportSettings(
+            orientation=orientation,
+            spacing=spacing,
+            margin=margin,
+            rows=rows,
+            columns=columns,
+            output_name=output_name,
+        )
+        self.destroy()
+
+    def _cancel(self) -> None:
+        self.result = None
+        self.destroy()