fix: second-wave bug fixes, security hardening, visual polish, UX improvements

Bug fixes:
- SRV-B1 through B5: server config, router, server_info, syscheck corrections
- BA-03 through BA-06: builder path and universal build cleanup (BLD-D1 through D3)
- Frontend WS race condition and useVisibleInterval hook fixed
- Drive-root path bug in PathForge resolved
- Upload error handling improved

Security:
- PathForge path traversal guard added
- Script injection escaping applied throughout

Visual (DV-01 through DV-15):
- Cyan design tokens and page headers standardised
- Dead CSS removed from Pages.css, PathTracerPage.css, wealth-deck.css
- SacredPageHeader deleted (replaced inline); sidebar version display fixed

UX:
- Emberwake request storm fixed (EmberwakePage.tsx)
- Help blurbs UH-01, UH-02, UH-06 added
- HelpTips wired into Crucible, Fleet (FleetGroupsStrip, FleetToolbar), Settings

Build:
- vite.config.ts: webroot auto-sync on build
- build_universal.go: universal build artifact cleanup
- PROBLEMS.md tracking updated

server/config.go

@@ -372,6 +372,11 @@ func (c *Config) AlertSettings() alerts.Settings {
 	})
 }
 
+// mergeConfig is the legacy unconditional merge used only as a fallback when no
+// field-presence map is available (i.e. never during API PUT). Boolean fields such
+// as UseTLS are blindly copied from src, meaning a zero-value src resets them to
+// false. Prefer mergeConfigExplicit for all partial-update paths — it only applies
+// a field when that key was explicitly present in the JSON payload.
 func mergeConfig(dst, src *Config) {
 	if src.Port != 0 {
 		dst.Port = src.Port