feat(login): dev-only prefill from VITE_ADMIN_EMAIL/PASSWORD

When import.meta.env.DEV is true, the login form's email and password
fields are populated from the corresponding env vars. Shaves the manual
re-typing during dev iteration.

Production builds get empty strings regardless of build-time env values:
the prefill is gated on import.meta.env.DEV (which Vite replaces with
literal `false` at build time, so the surrounding ternary tree-shakes
and the env values can't bleed into the prod bundle even if accidentally
set in the build env).

Files:
- src/vite-env.d.ts (new): ImportMetaEnv augmentation with the four
  VITE_* vars we use (admin email/password, dev directus/processor URLs).
  Gives proper typing under strict mode.
- src/ui/pages/login.tsx: devDefaults computed once at module scope from
  import.meta.env. Form's defaultValues uses it.
- .env.example: documents VITE_ADMIN_EMAIL and VITE_ADMIN_PASSWORD with
  examples; notes the prod-ignore guarantee.
- .gitignore: adds *.env (defensive — complements the existing *.local
  pattern). .env.example stays committable (doesn't end in .env).

.planning/phase-1-foundation/08-logout-flow.md

@@ -140,9 +140,10 @@ This is the right trade-off: logout that fails should _not_ leave the user appea
 
 **Bonus from this task** — caught a missing `"strict": true` in `tsconfig.app.json`. TanStack Router emits a `"strictNullChecks must be enabled"` conditional-type error in editors when strict mode is off; CI's `tsc -b` was lenient. Added `strict: true` (along with the existing strict-adjacent flags); typecheck still green.
 
-**Smoke check:** `pnpm typecheck`, `pnpm lint`, `pnpm format:check`, `pnpm build` all green. Bundle: 353KB main + same per-route chunks as 1.7 (login 37KB, _authed 1.4KB grew slightly with the LogoutButton). No measurable bundle impact from the logout orchestration.
+**Smoke check:** `pnpm typecheck`, `pnpm lint`, `pnpm format:check`, `pnpm build` all green. Bundle: 353KB main + same per-route chunks as 1.7 (login 37KB, \_authed 1.4KB grew slightly with the LogoutButton). No measurable bundle impact from the logout orchestration.
 
 **Browser smoke pending:**
+
 1. Sign in. Click "Sign out". Watch button show "Signing out…", then redirect to `/login`. Hard refresh on `/login` stays on `/login`.
 2. Sign in in tab A. Open tab B (same SPA). Sign out in tab A. Tab B's home page should redirect to `/login` on next interaction (or immediately, depending on whether the storage event triggers re-render).
 3. With DevTools "Network: offline", click sign out. Should still navigate to `/login` (server call fails, local state forced to anonymous).