refactor: rename packages and files to use 'flash' prefix for consistency

flash-extensions/flash-ext-web-bundler/docs/asset-sources.md

@@ -0,0 +1,22 @@
+# Asset Sources
+
+`flash-web-bundler` uses explicit source objects for production assets.
+
+Supported sources:
+
+- `FilesystemAssetsSource.of(Path)`
+- `ClasspathAssetsSource.of(String rootPrefix)`
+
+Builder shortcuts:
+
+- `.assetsFromFilesystem(Path.of("dist"))`
+- `.assetsFromClasspath("web/dist")`
+
+Classpath source requires `asset-manifest.json` generated at build time.
+The developer does not maintain this file manually.
+
+Production startup is fail-fast if:
+
+- manifest is missing
+- manifest is invalid
+- manifest points to missing resources