Refactor useGenerationForm to streamline model download handling

- Removed unnecessary isDownloading variable and related logic.
- Consolidated model download state reset to the finally block for improved clarity and reliability.
- Enhanced error handling by ensuring model download state is reset in case of failure.

docs/nixpacks.toml

@@ -0,0 +1,11 @@
+[phases.setup]
+nixPkgs = ["nodejs_20", "bun"]
+
+[phases.install]
+cmds = ["bun install"]
+
+[phases.build]
+cmds = ["bun run build"]
+
+[start]
+cmd = "bun run start"