Add per-movie attributes and per-category filename templates

src/constants.py

@@ -5,9 +5,8 @@ This module derives the app version and debug flag. The version is loaded from
 `pyproject.toml` (preferred) with a generated `src/_version.py` fallback for
 frozen/PyInstaller builds. Debug mode is controlled via `.env` (`ENV_DEBUG`).
 
-Note: per-feature constants (window size, tag colors, …) live in
-`src/core/constants.py`; this module is only the version/debug surface used by
-the build tooling and frozen builds.
+It is the single source of truth for app metadata used across the GUI and build
+tooling (`APP_NAME`, `APP_VERSION`/`VERSION`, `APP_TITLE`, `APP_VIEWPORT`).
 """
 
 import os
@@ -64,3 +63,6 @@ APP_TITLE: str = f"{APP_NAME} v{APP_VERSION}" + ("-DEV" if ENV_DEBUG else "")
 
 # Backwards-compatible alias used by prebuild.py
 VERSION: str = APP_VERSION
+
+# Default main-window geometry (used when no saved geometry exists)
+APP_VIEWPORT: str = "1000x700"