v0.4.0 - NIM installer + dashboard resilience

Hotfix (was v0.3.1):
- services.py: cache 'unreachable' per (host,user) for 25s so a dead Spark doesn't hang every /api/services call behind 6s ssh timeout
- ssh_run timeout reduced 10 -> 6s for docker_state probes
- hardware probe: shorter SSH timeout (6s), longer cache TTL for failures (25s)
- JS pollStatus retries loadModels() if state.models is empty (recovers from cold-start proxy timeout)
- Unreachable hardware card now includes troubleshooting steps (Spark Control cannot SSH into an unreachable Spark to restart it)

v0.4 NIM installer:
- nim.py module: curated SUGGESTED_NIMS list (Parakeet, Magpie, Riva) + NimManager that runs docker login nvcr.io + docker pull + docker run -d --gpus all -p PORT:PORT -v VOL:/opt/nim/.cache -e NGC_API_KEY -e ... --restart=unless-stopped + chown the volume to uid 1000 + restart. Streams all output via SSE; redacts the API key from log lines.
- custom_services.py: persists installed NIMs to /data/services-overrides.yaml so they appear in the services panel after install
- services.py: merges custom services into the panel
- /api/nim/catalog GET, /api/nim/install POST + GET/SSE
- /api/services/{name} DELETE for custom services
- UI: '+ Install NIM' button next to 'Always-on services'; modal lists curated images each with a 'Pick' button + a custom-image form; installation runs in a second dialog with phase + elapsed timer + collapsible log
- NGC API key field added to Configure Sparks (masked); injected as NGC_API_KEY env var into the container

Package: bump 0.4.0:0; main.ts adds SERVICES_OVERRIDES + NGC_API_KEY env vars

image/app/custom_services.py

@@ -0,0 +1,59 @@
+"""User-installed services persist in /data/services-overrides.yaml.
+
+Format:
+    custom:
+      - key: my-riva
+        kind: stt
+        host: <spark-2-ip>
+        user: <spark-user>
+        container: riva-asr
+        port: 8001
+        health_path: /health
+        image: nvcr.io/nim/nvidia/riva-multilingual:latest
+"""
+from __future__ import annotations
+import os
+from pathlib import Path
+import yaml
+
+
+def _path() -> str:
+    return os.environ.get("SERVICES_OVERRIDES", "/data/services-overrides.yaml")
+
+
+def load_custom_services() -> list[dict]:
+    try:
+        with open(_path()) as f:
+            data = yaml.safe_load(f) or {}
+    except FileNotFoundError:
+        return []
+    return data.get("custom") or []
+
+
+def add_custom_service(entry: dict) -> None:
+    p = _path()
+    Path(p).parent.mkdir(parents=True, exist_ok=True)
+    data: dict = {}
+    try:
+        with open(p) as f:
+            data = yaml.safe_load(f) or {}
+    except FileNotFoundError:
+        pass
+    custom = data.get("custom") or []
+    custom = [c for c in custom if c.get("key") != entry["key"]]
+    custom.append(entry)
+    data["custom"] = custom
+    with open(p, "w") as f:
+        yaml.safe_dump(data, f, sort_keys=False)
+
+
+def delete_custom_service(key: str) -> None:
+    p = _path()
+    try:
+        with open(p) as f:
+            data = yaml.safe_load(f) or {}
+    except FileNotFoundError:
+        return
+    data["custom"] = [c for c in (data.get("custom") or []) if c.get("key") != key]
+    with open(p, "w") as f:
+        yaml.safe_dump(data, f, sort_keys=False)