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/templates/fragments/audit_rows.html

@@ -1,7 +1,7 @@
 {{define "audit_rows"}}
 {{range .Events}}
-<tr>
-  <td class="text-small text-muted">{{formatTime .EventTime}}</td>
+<tr class="clickable-row" onclick="window.location='/audit/{{.ID}}'">
+  <td class="text-small text-muted"><a href="/audit/{{.ID}}">{{formatTime .EventTime}}</a></td>
   <td><code style="font-size:.8rem">{{.EventType}}</code></td>
   <td class="text-small text-muted">{{if .ActorUsername}}{{.ActorUsername}}{{else}}&mdash;{{end}}</td>
   <td class="text-small text-muted">{{if .TargetUsername}}{{.TargetUsername}}{{else}}&mdash;{{end}}</td>