fix(stats): unambiguous chart x-labels + unit-carrying tooltips

The daily charts' x-axis labels were bare MM-DD ('10-15', '10-16') — on
the Listening per Day chart (y in hours) those read as hour values, which
is exactly the '10-16 hours a day' misread that prompted this. Labels now
spell the month ('Oct 15') and every chart's tooltip carries its unit
(min / pages / hrs). main.js?v=5

templates/header.templ

@@ -213,7 +213,7 @@ templ Header(user User, currentPath string) {
 		</header>
 		<!-- module bundle; ?v=<commit-ish stamp> busts stale intermediate
 		     builds across app restarts (browser caches are keyed by URL) -->
-		<script type="module" src="/static/main.js?v=4"></script>
+		<script type="module" src="/static/main.js?v=5"></script>
 	</div>
 }