fix: proper styling for global time tracker popup (#10827)

- Resolves forgejo/forgejo#10819
- CSS from tippy is overriding the style specifically for active-stopwatch-popup because of strange/incorrect HTML structure, so override it via `!important`.

## Test
1. Start timer on any issue.
2. See that the styling is okay in the global time tracker popup in the navbar.

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/10827
Reviewed-by: 0ko <0ko@noreply.codeberg.org>
Reviewed-by: Beowulf <beowulf@beocode.eu>
Co-authored-by: Gusted <postmaster@gusted.xyz>
Co-committed-by: Gusted <postmaster@gusted.xyz>

web_src/css/modules/tippy.css

@@ -168,3 +168,8 @@
 .tippy-svg-arrow-inner {
   fill: var(--color-body);
 }
+
+/* Stopwatch popup needs extra help with overriding tippy's styling. */
+.tippy-box .active-stopwatch-popup {
+  display: flex !important;
+}