feat(frontend): post collected samples to /api/v1/reports (closes #53)

A Reporter beside AppState POSTs a JSON delta report of each host's
unreported, non-paused samples to the same-origin /api/v1/reports every
reportInterval (default 60s). buildReport is an exported pure function of
host state; init() runs only when #app exists, so a test can import it.
Per-host marks advance only on a delivered POST and never move backwards;
only one POST is in flight, abandoned after half the interval, so a slow
backend cannot cause re-sent samples. Failure is quiet and never blocks
probing.

The client id falls back to crypto.getRandomValues where crypto.randomUUID
is missing (plain HTTP to a non-localhost host). vite.config.js proxies
/api to 127.0.0.1:8080 for yarn dev.

Model: opus-5-5

vite.config.js

@@ -7,6 +7,13 @@ const commitFull = execSync("git rev-parse HEAD").toString().trim();
 
 export default defineConfig({
     plugins: [tailwindcss()],
+    server: {
+        // Proxy /api to a locally running netwatch-server so `yarn dev`
+        // exercises the real report-posting path.
+        proxy: {
+            "/api": "http://127.0.0.1:8080",
+        },
+    },
     define: {
         __COMMIT_HASH__: JSON.stringify(commitHash),
         __COMMIT_FULL__: JSON.stringify(commitFull),