fix(fonts): self-host the bold weights; delete orphaned reading.css

A. Removing the Google Fonts links left font-weight:700 (306 uses on
JetBrains Mono, 50 on Inter) and 800 (68 on JetBrains Mono) with no real
face, so every one rendered synthetic bold — worst in code blocks, which
is most of the technical content.

Adds @fontsource/inter/700 and @fontsource/jetbrains-mono/700 + /800
alongside the existing imports in global.css. All three packages were
already installed at ^5.2.8 and ship every weight needed; nothing new to
install, no family substituted, no variable-font fallback.

Sora was checked, not assumed: it is used only at 600 and 700, both
already imported. No change.

Two weights remain unimported by design, and neither synthesises:
JetBrains Mono 400 (2 uses) resolves to the real 500 face, and 600 (10
uses) now resolves to the real 700 face. Adding them would cost ~40 KB
to change nothing visible. Flagged rather than silently added.

Added transfer: 65 KB across 3 latin faces (Inter 700 23 KB, JBM 700
21 KB, JBM 800 20 KB). woff2 is Brotli-compressed internally, so file
size is transfer size. Other subsets (cyrillic/greek/vietnamese/latin-ext)
are declared with unicode-range and are not fetched on English pages.

@font-face rules 41 -> 60, all 60 carrying font-display:swap.
No preloads added. No other CSS touched.

B. Deletes src/styles/reading.css. It was imported nowhere — zero
references in src/, astro.config.mjs or package.json — and had never been
committed, so it was not a clean-clone deploy risk: nothing imported it,
so working-tree and clean-clone builds produced identical CSS. It was
dead weight surfacing in every status report.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Author: lsb11

src/styles/global.css

@@ -3,7 +3,10 @@
 @import "@fontsource/inter/400.css";
 @import "@fontsource/inter/500.css";
 @import "@fontsource/inter/600.css";
+@import "@fontsource/inter/700.css";
 @import "@fontsource/jetbrains-mono/500.css";
+@import "@fontsource/jetbrains-mono/700.css";
+@import "@fontsource/jetbrains-mono/800.css";
 
 @import "tailwindcss";