feat: environment model + deployment tracking (phase 3a)

- Environment/Deployment XORM models + migration 010
- Full CRUD API: GET/POST/PATCH/DELETE /environments + /deployments
- Deployment status update endpoint, publishes deployment.* NATS events
- EnvironmentsPage with deploy cards, history accordion, deploy modal
- Sidebar Environments nav item between Pipelines and Settings
- Repo page deployment status badges (env name + SHA pill per
  environment)
- Environment/Deployment types in types/api.ts + environments.ts query
  hooks

frontend/src/App.tsx

@@ -37,6 +37,7 @@ const PRsPage           = lazy(() => import('./pages/PRsPage'))
 const PipelinesPage     = lazy(() => import('./pages/PipelinesPage'))
 const PipelineRunPage      = lazy(() => import('./pages/PipelineRunPage'))
 const RepoPipelinesPage    = lazy(() => import('./pages/RepoPipelinesPage'))
+const EnvironmentsPage     = lazy(() => import('./pages/EnvironmentsPage'))
 const ProfilePage       = lazy(() => import('./pages/ProfilePage'))
 const ExplorePage       = lazy(() => import('./pages/ExplorePage'))
 const SettingsPage      = lazy(() => import('./pages/SettingsPage'))
@@ -85,6 +86,7 @@ export default function App() {
               <Route path="repos/:owner/:repo/pulls/new"           element={<S><CreatePRPage /></S>} />
               <Route path="repos/:owner/:repo/pulls/:prId"         element={<S><PRDetailPage /></S>} />
               <Route path="repos/:owner/:repo/pipelines"           element={<S><RepoPipelinesPage /></S>} />
+              <Route path="repos/:owner/:repo/environments"        element={<S><EnvironmentsPage /></S>} />
               <Route path="repos/:owner/:repo/runs/:runId"         element={<S><PipelineRunPage /></S>} />
 
               <Route path="starred"   element={<S><StarredPage /></S>} />