feat(ext-vite): replace the web bundler with a Vite extension and its Maven plugin

flash-ext-vite runs Vite's dev server in DEV and otherwise serves the build from the
classpath, read straight from the directory or jar with no manifest. The Maven plugin
flash-ext-vite-maven-plugin builds the frontend at prepare-package and packages it
there, so mvn package makes a jar that serves its own frontend and mvn test needs no
Node. Three overrides remain (root, devPort, basePath); the package manager is read
from the nearest lockfile.

Serving fixes what the bundler got wrong: Vite's hashed files under assets/ are
cached as immutable instead of revalidated, HEAD reports the real Content-Length, a
missing asset is a 404 instead of the index, 304s carry ETag and Cache-Control, and
gzip respects q=0 and is prepared at boot. Every response header is pre-encoded, so
serving allocates nothing, which is what Response.type(byte[]) is for. Vite stops
with the app through onClose, and a lockfile change reinstalls before restarting.

The modes, strategies, logging and command-safety options, the asset-source
abstraction, the manifest and the Jackson dependency are gone: 1,535 lines of main
code become 480, plus 84 for the plugin.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

AGENTS.md

@@ -37,7 +37,7 @@ Format: `<type>(<scope>): <short description>`
 | `ci` | Changes to GitHub Actions workflows |
 
 Allowed scopes: `core`, `testing`, `ext-jackson`, `ext-openapi`, `ext-oidc`, `ext-routeviewer`,
-`ext-view-core`, `ext-view-jte`, `ext-view-thymeleaf`, `ext-limiter`, `ext-web-bundler`,
+`ext-view-core`, `ext-view-jte`, `ext-view-thymeleaf`, `ext-limiter`, `ext-vite`,
 `ext-mcp`, `ext-validation`, `ext-scheduler`, `ext-data-core`, `ext-data-jdbc`, `ext-data-hibernate`,
 `ext-cache-core`, `ext-cache-caffeine`, `release`, `deps`, `ci`.