Restyle the web UI in a light theme, step 1: theme, top nav, demo trading

Follow the Stitch "Daylight" design: light canvas, white panels with
hairline borders, deep cyan primary, Inter for UI text and JetBrains Mono
for numbers (bundled via @fontsource-variable).

- Override Element Plus variables in one place and derive light/dark
  shades with color-mix; pages use the UnoCSS Tailwind palette.
- Replace the sidebar with a horizontal top navigation bar.
- Rebuild the demo trading page: status panel with metric tiles,
  positions table, and a three-column layout (symbols, plan card,
  open orders and timeline); restyle the analysis drawer.
- Fix the stale risk wording in the trading capital dialog.

web/pnpm-lock.yaml

@@ -11,6 +11,12 @@ importers:
       '@element-plus/icons-vue':
         specifier: ^2.3.2
         version: 2.3.2([email protected]([email protected]))
+      '@fontsource-variable/inter':
+        specifier: ^5.3.0
+        version: 5.3.0
+      '@fontsource-variable/jetbrains-mono':
+        specifier: ^5.3.0
+        version: 5.3.0
       axios:
         specifier: ^1.20.0
         version: 1.20.0([email protected])
@@ -303,6 +309,12 @@ packages:
   '@floating-ui/[email protected]':
     resolution: {integrity: sha512-HpCo8tmWzLVad5s2d19EhAz5zqrrQ6s69qd6moPMQvkOuSwDT1YgRfWSVuc4ennqrgv3OHppiOGMQ7oC13yIww==}
 
+  '@fontsource-variable/[email protected]':
+    resolution: {integrity: sha512-OupL48va4JNofb97w6NYeF9S7W/kHNKM0Er8Dem5nqi4jeOLrVJDoE8tZEpnMJmtkvNbB1EIPPwHcdkF6b1oUA==}
+
+  '@fontsource-variable/[email protected]':
+    resolution: {integrity: sha512-F32xpS2NsGYoQi2ADSkKTgpJj7ozajsGgDJ8woTnqjmIB+dxDIqImjl4pXZVEExu8UFZ2ndhmX18EBS/hdz3Lw==}
+
   '@humanfs/[email protected]':
     resolution: {integrity: sha512-UhXNm+CFMWcbChXywFwkmhqjs3PRCmcSa/hfBgLIb7oQ5HNb1wS0icWsGtSAUNgefHeI+eBrA8I1fxmbHsGdvA==}
     engines: {node: '>=18.18.0'}
@@ -2889,6 +2901,10 @@ snapshots:
 
   '@floating-ui/[email protected]': {}
 
+  '@fontsource-variable/[email protected]': {}
+
+  '@fontsource-variable/[email protected]': {}
+
   '@humanfs/[email protected]':
     dependencies:
       '@humanfs/types': 0.15.0