fix: eliminate deprecated cyan, glass-border, and off-palette colors site-wide

- Replace all rgba(6,182,212,...) cyan focus borders and accents with
  rgba(249,115,22,...) ember orange across 21+ component files
- Remove all var(--glass-border) references (undefined variable) with
  var(--color-border-default) across 24 files
- Remove deprecated blur orbs and glass-morphism effects from
  SurveyPage, SurveyThankYouPage, and LoginPage
- Migrate landing.css from hardcoded hex to CSS custom properties
  (~97 replacements for single-source theming)
- Fix off-palette grays in FlowPilotAnalyticsPage chart styling
  (#8891a0 → #848b9b, #18191f → var(--color-bg-card))
- Update stale comments: "cyan brand" → "accent brand" in GlowEdge,
  "gradient cyan square" → "gradient orange square" in BrandLogo
- Rename glow-cyan SVG filter ID to glow-accent
- Fix category color comment: "cyan" → "deep orange"

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/pages/account/ChatRetentionSettingsPage.tsx

@@ -74,7 +74,7 @@ export default function ChatRetentionSettingsPage() {
               min={1}
               max={365}
               className="w-full rounded-xl border bg-card text-foreground text-sm px-4 py-2.5 focus:outline-hidden focus:border-primary/30"
-              style={{ borderColor: 'var(--glass-border)' }}
+              style={{ borderColor: 'var(--color-border-default)' }}
             />
             <p className="text-xs text-muted-foreground mt-1">
               Chats older than this will be automatically deleted (1-365 days)
@@ -92,7 +92,7 @@ export default function ChatRetentionSettingsPage() {
               min={10}
               max={10000}
               className="w-full rounded-xl border bg-card text-foreground text-sm px-4 py-2.5 focus:outline-hidden focus:border-primary/30"
-              style={{ borderColor: 'var(--glass-border)' }}
+              style={{ borderColor: 'var(--color-border-default)' }}
             />
             <p className="text-xs text-muted-foreground mt-1">
               When this limit is exceeded, oldest unpinned chats are deleted