Rename admin routes to ISAC

docs/DESIGN_SYSTEM.md

@@ -435,7 +435,7 @@ Do not communicate state by color alone; include a label, icon, or pattern.
 
 ## Adding a new admin module
 
-1. Add the route beneath `src/routes/admin`.
+1. Add the route beneath `src/routes/isac`.
 2. Register it in the admin layout navigation.
 3. Start with the module toolbar and KPI row.
 4. Reuse dashboard editor and table classes.

docs/architecture.md

@@ -181,7 +181,11 @@ specialized workflow rather than inferred database writes.
 
 # System metrics
 
-The read-only `/admin/metrics` route requires `metrics.view` and collects a
+ISAC uses `/isac` as its canonical route namespace. The server permanently
+redirects legacy `/admin` URLs to their matching `/isac` location so old
+notifications and external bookmarks remain usable.
+
+The read-only `/isac/metrics` route requires `metrics.view` and collects a
 point-in-time process-local health snapshot. Node and operating-system APIs
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