refactor(operator): derive env badge from hostname, not from user choice

A toggle-able env badge is a sticker, not a safety signal. Move env to
useEnv() which reads window.location.hostname:
  *.local / localhost → 'dev'
  *staging* → 'staging'
  everything else → 'prod' (safest default)

- New composable: apps/operator/composables/useEnv.ts
- Topbar reads useEnv() instead of useTweaks().env
- useTweaks loses the env field; hydrate strips it from stale
  localStorage payloads so old entries don't break
- TweaksPanel: env section removed (theme + density remain)
- Settings: env section removed from Appearance; added a read-only
  Environment row to the Profile card showing the detected env +
  hostname source ("auto-detected from operator.dezky.local")

apps/operator/components/TweaksPanel.vue

@@ -1,10 +1,10 @@
 <script setup lang="ts">
-// Floating cosmetic-tweaks panel. Lives in the bottom-right corner. Lets the
-// operator flip theme/density/env without touching settings pages. All three
-// are pure-cosmetic — env in particular is just a colored chip in the topbar,
-// not a real environment switch.
+// Floating cosmetic-tweaks panel. Lives in the bottom-right corner. Quick
+// theme + density toggle without leaving the page. The env badge is NOT
+// here — it's derived from the hostname (see useEnv) so the operator can
+// trust it as a real environment signal, not a sticker they flipped.
 
-const { state, setTheme, setDensity, setEnv } = useTweaks()
+const { state, setTheme, setDensity } = useTweaks()
 const open = ref(false)
 </script>
 
@@ -39,15 +39,6 @@ const open = ref(false)
           </div>
         </section>
 
-        <section>
-          <label class="row-label">Env badge</label>
-          <div class="seg three">
-            <button :class="{ on: state.env === 'prod' }" type="button" @click="setEnv('prod')">PROD</button>
-            <button :class="{ on: state.env === 'staging' }" type="button" @click="setEnv('staging')">STAGING</button>
-            <button :class="{ on: state.env === 'dev' }" type="button" @click="setEnv('dev')">DEV</button>
-          </div>
-        </section>
-
         <footer>
           <Mono dim>// cosmetic only — saved to localStorage</Mono>
         </footer>
@@ -129,7 +120,6 @@ section { display: flex; flex-direction: column; gap: 6px; }
   border: 1px solid var(--border);
   border-radius: 7px;
 }
-.seg.three { grid-template-columns: 1fr 1fr 1fr; }
 .seg button {
   appearance: none;
   border: 0;