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

A Reporter beside AppState POSTs each host's unreported, non-paused
samples to /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 the module. A per-host mark
advances only on a delivered POST. At most one report POST is pending at
a time and it is abandoned after half the interval, so a slow POST never
overlaps the next report and a mark never moves backwards. The samples of
an abandoned POST are sent again at the next interval, so a backend that
stored them but answered late receives them twice. Failure is quiet and
never blocks probing. vite.config.js proxies /api 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),