Make button labels visible on non-green buttons

The global `button` rule pairs a green background with white text. Any
variant that overrode the background without also setting `color` kept
the white text and rendered invisible against a light background.

Four controls were affected, all measured white-on-white or
white-on-light-grey: the calendar header's prev/next arrows, the
calendar's override-mode toggle, the red-days list's year navigation,
and the modal close button.

Each now declares its own `color: var(--c-text)`. Using the variable
rather than a literal means the high-contrast media query in
responsive.css, which redefines --c-text to #000, still applies.

Also adds the hover and focus-visible states the Settings and
vacation-days Save buttons were missing entirely -- they were the only
green buttons in the app that did not react to the pointer. Hover is
scoped with :not(:disabled) so a button disabled mid-save stays inert.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01RXMhc9nT6sNz1SL4j8dznL

frontend/src/pages/calendar.css

@@ -16,6 +16,7 @@
   min-height: 36px;
   padding: 8px 12px;
   background: none;
+  color: var(--c-text);
   border: 1px solid #d0d0d0;
   border-radius: 4px;
   font-size: 18px;
@@ -373,6 +374,7 @@
   border: 1px solid #d0d0d0;
   border-radius: 4px;
   background: #fff;
+  color: var(--c-text);
   cursor: pointer;
   font-size: 13px;
   transition: background-color 0.2s, border-color 0.2s, color 0.2s;

frontend/src/styles/components.css

@@ -371,18 +371,46 @@ button.ghost:hover:not(:disabled) {
   font-size: var(--fs-sm);
 }
 
+.settings-page__button:not(:disabled):hover {
+  background-color: #1f5a3b;
+}
+
+.settings-page__button:focus-visible {
+  outline: 2px solid var(--c-accent);
+  outline-offset: 2px;
+}
+
 .settings-page__button--secondary {
   background-color: transparent;
   color: var(--c-text);
   border: 1px solid var(--c-border);
 }
 
+.settings-page__button--secondary:not(:disabled):hover {
+  background-color: var(--c-bg);
+}
+
+.settings-page__button--secondary:focus-visible {
+  outline: 2px solid var(--c-accent);
+  outline-offset: 2px;
+}
+
 .settings-page__button--danger {
   background-color: var(--c-danger-weak);
   color: var(--c-danger);
   border: 1px solid var(--c-danger);
 }
 
+.settings-page__button--danger:not(:disabled):hover {
+  background-color: var(--c-danger);
+  color: white;
+}
+
+.settings-page__button--danger:focus-visible {
+  outline: 2px solid var(--c-accent);
+  outline-offset: 2px;
+}
+
 /* Vacation Days Table (multi-year) */
 .vacation-days-table {
   width: 100%;
@@ -434,6 +462,15 @@ button.ghost:hover:not(:disabled) {
   white-space: nowrap;
 }
 
+.vacation-days-table__save:not(:disabled):hover {
+  background-color: #1f5a3b;
+}
+
+.vacation-days-table__save:focus-visible {
+  outline: 2px solid var(--c-accent);
+  outline-offset: 2px;
+}
+
 .vacation-days-table__empty {
   color: var(--c-text-muted);
   font-size: var(--fs-sm);
@@ -705,6 +742,7 @@ legend {
   border: 1px solid var(--c-border);
   border-radius: var(--radius);
   background-color: var(--c-surface);
+  color: var(--c-text);
   cursor: pointer;
 }
 

frontend/src/styles/modals.css

@@ -49,6 +49,7 @@
 .modal__close {
   background: none;
   border: none;
+  color: var(--c-text);
   font-size: var(--fs-lg);
   cursor: pointer;
   padding: 0;