feat: show which model is currently loaded in Ollama

- /api/loaded backend endpoint proxies Ollama /api/ps and returns
  {models: [{name, expires_at}]}
- Status line under the controls shows "Hot: gemma2:9b — unloads in 4m"
  with a glowing orange dot, or "No model loaded" in muted style
- Loaded models in the dropdown get a "● " prefix
- Refreshes on page load, after every translation, and 500ms after the
  user pauses typing in the input box

app.py

@@ -49,6 +49,23 @@ async def list_models() -> list[str]:
     return sorted(names)
 
 
+@app.get("/api/loaded")
+async def loaded_models() -> dict[str, list[dict[str, str | None]]]:
+    """Models currently resident in Ollama's memory (from /api/ps)."""
+    async with httpx.AsyncClient(timeout=5) as client:
+        try:
+            r = await client.get(f"{OLLAMA_URL}/api/ps")
+            r.raise_for_status()
+        except httpx.HTTPError as e:
+            raise HTTPException(502, f"Ollama unreachable: {e}") from e
+    return {
+        "models": [
+            {"name": m["name"], "expires_at": m.get("expires_at")}
+            for m in r.json().get("models", [])
+        ]
+    }
+
+
 @app.post("/api/translate")
 async def translate(req: TranslateRequest) -> StreamingResponse:
     text = req.text.strip()