feat(slint): +1px typography scale and shared paragraph-preserving strip_html

Two text-side refinements to the artist + album views.

Typography:
  - Bumps every scale level by 1px so body text reads at 15px instead
    of 14px (legal 13, link 14, body/subtitle 15, button 17, heading
    19, title 25, wordmark 29). All views adopt the new scale through
    the existing tokens — the artist + album descriptions feel
    noticeably more readable without per-component overrides.

strip_html (new shared module `crates/qbz-slint/src/strip_html.rs`):
  - Single implementation now used by both album::map_album and
    artist::map_artist for editorial copy (reviews, biographies).
    The previous album-local helper handled only <br> and </p>; the
    artist-local helper handled neither, so multi-paragraph
    biographies collapsed into one wall of text.
  - <br>, <br/>, <br /> (any case + spacing) -> \n. </p>, </P> ->
    \n\n. Stripped tags like <strong>, <em>, <a> still leave their
    text inline. (Slint's `Text` is single-style, so true inline
    bold/italic isn't possible without splitting into multiple Text
    elements — deferred.)
  - Broader entity table: amp/lt/gt/quot/apos/nbsp/copy/reg/mdash/
    ndash/hellip/curly quotes plus numeric copy variants.
  - Runs of 3+ newlines collapse to a paragraph break so stacked tags
    don't blow the layout open. Unit tests for each path.

cc

crates/qbz-slint/ui/foundation/typography.slint

@@ -1,14 +1,14 @@
 // Typography scale — font sizes and weights.
 
 export global Typography {
-    out property <length> legal: 12px;
-    out property <length> link: 13px;
-    out property <length> body: 14px;
-    out property <length> subtitle: 14px;
-    out property <length> button: 16px;
-    out property <length> heading: 18px;
-    out property <length> title: 24px;
-    out property <length> wordmark: 28px;
+    out property <length> legal: 13px;
+    out property <length> link: 14px;
+    out property <length> body: 15px;
+    out property <length> subtitle: 15px;
+    out property <length> button: 17px;
+    out property <length> heading: 19px;
+    out property <length> title: 25px;
+    out property <length> wordmark: 29px;
 
     out property <int> regular: 400;
     out property <int> medium: 500;