Add Dashboards UI: PromQL-backed bar/line/pie panels saved per profile (ticket 014)

Backend: replace Profile.dashboards' opaque JSON stub with typed
Dashboard/Panel structs, add ProfileStore CRUD (create/save/list/delete
dashboard) and matching /api/settings/profiles/:name/dashboards[/:id] routes,
with tests covering the HTTP round trip and persistence across a simulated
restart.

Frontend: add recharts (lightweight, React 19-compatible) and a Dashboards
component with a dashboard builder (create dashboards, add/remove/edit panels
with a PromQL query + chart type), live per-panel previews that respect the
active time range and show malformed-query errors inline instead of crashing,
and load/save wired to the new profile-backed persistence.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XFUNZwCvz3kcod3352ZR2o

webapp/src/App.tsx

@@ -3,8 +3,8 @@ import { NavMenu } from './components/NavMenu'
 import { FilterBar } from './components/FilterBar'
 import { LogTimeline, type TimeRange } from './components/LogTimeline'
 import { LogPreview } from './components/LogPreview'
-import { ComingSoon } from './components/ComingSoon'
 import { Metrics } from './components/Metrics'
+import { Dashboards } from './components/Dashboards'
 import { fetchLogs, fetchStats, fetchTimeline, type LogEntry, type Stats, type TimelineBucket } from './lib/api'
 
 const POLL_MS = 2000
@@ -56,7 +56,7 @@ export default function App() {
         <LogTimeline buckets={buckets} range={range} onSelectRange={setRange} />
         <LogPreview logs={logs} />
         <Metrics range={range} />
-        <ComingSoon title="Dashboards" />
+        <Dashboards range={range} />
       </div>
     </div>
   )