feat(shortcut): Add keyboard shortcuts for repository file and code search

Add GitHub-like keyboard shortcuts for repository navigation:
- Press 'T' to focus the "Go to file" search input
- Press 'S' to focus the "Search code" input
- Press 'Escape' to blur focused search inputs

Both search inputs display a keyboard hint (kbd element) showing
the available shortcut. The hint hides when the input is focused
or has a value.

Includes unit tests and e2e tests for the new functionality.

web_src/css/repo.css

@@ -2064,3 +2064,42 @@ tbody.commit-list {
 .branch-selector-dropdown .scrolling.menu .loading-indicator {
   height: 4em;
 }
+
+/* Keyboard shortcut hint styles for repo search inputs */
+.repo-code-search-input-wrapper {
+  position: relative;
+}
+
+.repo-code-search-input-wrapper input {
+  padding-right: 32px !important;
+}
+
+.repo-search-shortcut-hint {
+  position: absolute;
+  right: 40px; /* account for the search button */
+  top: 50%;
+  transform: translateY(-50%);
+  display: inline-block;
+  padding: 2px 6px;
+  font-size: 11px;
+  line-height: 14px;
+  color: var(--color-text-light-2);
+  background-color: var(--color-box-body);
+  border: 1px solid var(--color-secondary);
+  border-radius: var(--border-radius);
+  box-shadow: inset 0 -1px 0 var(--color-secondary);
+  pointer-events: none;
+  z-index: 1;
+}
+
+/* Override Fomantic UI action input styles for file search - need high specificity */
+.repo-file-search-input-wrapper.ui.input input,
+.repo-file-search-input-wrapper.ui.input input:hover {
+  border-right: 1px solid var(--color-input-border) !important;
+  border-top-right-radius: 0.28571429rem !important;
+  border-bottom-right-radius: 0.28571429rem !important;
+}
+
+.repo-file-search-input-wrapper.ui.input input:focus {
+  border-color: var(--color-primary) !important;
+}