fix heading colors on dark-OS systems, increase logo size

The heading color override (bare h1 selector, specificity 0,0,1) was
losing to Pico's theme-scoped heading rules ([data-theme=light] h1,
specificity 0,1,1). On systems with prefers-color-scheme: dark, Pico's
dark heading colors (#f0f1f3 — near white) leaked through, making
headings invisible on the light background.

Fix: scope heading overrides under [data-theme="light"] to match Pico's
specificity. Also bump nav logo from 24px to 32px, footer to 24px.

Visual tests now run with color_scheme="dark" to catch this class of bug.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

padelnomics/tests/test_visual.py

@@ -92,8 +92,11 @@ def browser():
 
 @pytest.fixture
 def page(browser):
-    """Create a new browser page with consistent viewport."""
-    pg = browser.new_page(viewport={"width": 1280, "height": 900})
+    """Create a page with dark OS preference to catch theme leaks."""
+    pg = browser.new_page(
+        viewport={"width": 1280, "height": 900},
+        color_scheme="dark",
+    )
     yield pg
     pg.close()