Fix grpcserver rate limiter: move to Server field

The package-level defaultRateLimiter drained its token bucket
across all test cases, causing later tests to hit ResourceExhausted.
Move rateLimiter from a package-level var to a *grpcRateLimiter field
on Server; New() allocates a fresh instance (10 req/s, burst 10) per
server. Each test's newTestEnv() constructs its own Server, so tests
no longer share limiter state.

Production behaviour is unchanged: a single Server is constructed at
startup and lives for the process lifetime.

web/embed.go

@@ -0,0 +1,13 @@
+// Package web provides embedded filesystem access to the web UI assets
+// (HTML templates and static files). The embed directives must live in
+// this package because Go's //go:embed does not allow ".." path components;
+// internal/ui imports these variables instead.
+package web
+
+import "embed"
+
+//go:embed all:templates
+var TemplateFS embed.FS
+
+//go:embed all:static
+var StaticFS embed.FS