Settle on one visual language

The interface had drifted into two of everything. The calendar and its
popovers were built around a blue accent the rest of the app had long since
replaced with green, five different sizes served the same class of small
label, and page sections were a stack of identical bordered cards that gave
no sense of what mattered most. Sections now separate by space and a hairline,
the overview leads with its headline figure at a size that says so, and the
palette, type scale and spacing live in one place as variables rather than
scattered literals.

Two things were not styled at all. The sign-in screen was an unstyled form in
the top-left corner, and the tip cards had no rules whatsoever despite their
markup already carrying a severity, so every tip rendered identically with a
plain green square for its dismiss control.

The calendar was also unusable on a narrow screen: the preset rail never
collapsed and covered the last three columns of the grid.

frontend/src/pages/Dashboard.tsx

@@ -229,23 +229,17 @@ export function Dashboard(): ReactNode {
 
         {age4Bars.length > 0 && <Age4Bars bars={age4Bars} />}
 
-        <section className="dashboard__section">
-          <div style={{ display: 'flex', gap: '10px' }}>
-            <button
-              onClick={handleFetchFK}
-              disabled={!selectedChildId}
-              style={{ padding: '0.5rem 1rem', cursor: selectedChildId ? 'pointer' : 'not-allowed' }}
-            >
-              {t('dashboard.fetchFromFk')}
-            </button>
-            <button
-              onClick={() => setShowManualFetchModal(true)}
-              disabled={!selectedChildId}
-              style={{ padding: '0.5rem 1rem', cursor: selectedChildId ? 'pointer' : 'not-allowed' }}
-            >
-              {t('dashboard.enterManually')}
-            </button>
-          </div>
+        <section className="dashboard__section dashboard__fetch-actions">
+          <button onClick={handleFetchFK} disabled={!selectedChildId}>
+            {t('dashboard.fetchFromFk')}
+          </button>
+          <button
+            onClick={() => setShowManualFetchModal(true)}
+            disabled={!selectedChildId}
+            className="button--secondary"
+          >
+            {t('dashboard.enterManually')}
+          </button>
         </section>
 
         {selectedChild && (