feat(redesign): aurora foundation — tokens, glass sidebar, dashboard

Foundation pass on the Aurora redesign:

- app.css: full token swap to lavender/orchid/mint/sky pastel palette,
  vivid aurora gradient backdrop, frosted glass surface tokens, two
  themes (Aurora dark + Pearl light), shadow recipe for floating glass.
- fonts: add Geist Sans / Geist Mono / Newsreader, drop DM Sans usage
  (legacy fontsource entries kept in package.json until full migration).
- layout.svelte: sidebar becomes a floating glass rail with a conic-
  gradient brand orb, Newsreader italic 'Bridge' wordmark, soft glass
  hovers on nav links, gradient active indicator, gradient user avatar.
- Card.svelte: glass surface + inner highlight + soft hover lift.
- PageHeader.svelte: Newsreader serif display title.
- +page.svelte (dashboard): stat cards become glass with colored
  accent 'orb', event timeline gets soft glass rows + slide-on-hover.

Build clean (0 errors, pre-existing a11y warnings unchanged).
Other pages still inherit old chrome via shared tokens but will need
component-specific passes; tracked separately.

frontend/package.json

@@ -35,7 +35,10 @@
 		"@codemirror/theme-one-dark": "^6.1.3",
 		"@codemirror/view": "^6.40.0",
 		"@fontsource/dm-sans": "^5.2.8",
+		"@fontsource/geist-mono": "^5.2.7",
+		"@fontsource/geist-sans": "^5.2.5",
 		"@fontsource/jetbrains-mono": "^5.2.8",
+		"@fontsource/newsreader": "^5.2.10",
 		"@mdi/js": "^7.4.47",
 		"codemirror": "^6.0.2"
 	}