feat(studio): first-run UX, recovery affordances, l10n, bundled fonts

- Connection-aware Welcome: when the hub is down, show a hero with a
  primary "Start hub" CTA + install fallback instead of a dead,
  all-unchecked onboarding checklist (the first-run cliff).
- Actionable binary-not-found (file picker + install link, not a
  "set FAI_BIN" dead end) and a connect-failure banner after
  repeated failed health polls.
- Localize six hardcoded English error/toast clusters (DE+EN ARB).
- Bundle Inter + JetBrains Mono as assets; drop the runtime
  google_fonts fetch (air-gap / KRITIS safe, no font-swap flash).

Signed-off-by: flemming-it <stefan.a.flemming@googlemail.com>

lib/l10n/app_en.arb

@@ -1523,5 +1523,79 @@
     "placeholders": {
       "error": {"type": "String"}
     }
-  }
+  },
+  "welcomeHubDownTitle": "The hub isn't running yet",
+  "welcomeHubDownBody": "Studio talks to a local hub — the engine that loads modules and runs flows. It isn't reachable right now. Start it to begin.",
+  "welcomeHubDownStart": "Start hub",
+  "welcomeHubDownStarting": "Starting…",
+  "welcomeHubDownDocsLink": "Can't start it? Read the getting-started guide",
+  "welcomeHubDownEndpoint": "Endpoint: {endpoint}",
+  "@welcomeHubDownEndpoint": {
+    "placeholders": {
+      "endpoint": {"type": "String"}
+    }
+  },
+  "daemonStartRequested": "Daemon start requested. Reconnecting…",
+  "daemonStartFailed": "Could not start daemon: {detail}",
+  "@daemonStartFailed": {
+    "placeholders": {
+      "detail": {"type": "String"}
+    }
+  },
+  "faiBinaryNotFound": "Could not find the `fai` program on this machine.",
+  "faiBinaryNotFoundHint": "Install the F∆I platform, or point Studio at an existing `fai` binary.",
+  "faiBinaryLocateButton": "Locate `fai` binary…",
+  "faiBinaryInstallDocsButton": "Open install guide",
+  "faiBinaryPickerTitle": "Select the `fai` binary",
+  "faiBinarySetOk": "Using `fai` binary at {path}",
+  "@faiBinarySetOk": {
+    "placeholders": {
+      "path": {"type": "String"}
+    }
+  },
+  "sysAiFixParse": "The provider sent a response in an unexpected format. Providers that aren't OpenAI-compatible may need a translation proxy.",
+  "sysAiFixUnknown": "Unexpected failure ({kind}). See the System AI documentation.",
+  "@sysAiFixUnknown": {
+    "placeholders": {
+      "kind": {"type": "String"}
+    }
+  },
+  "sysAiFixDisabled": "Configure System AI in Settings (Cmd+,) → System AI panel.",
+  "sysAiFixEnvMissing": "The API-key environment variable is empty. Set it in your shell, then restart the daemon.",
+  "sysAiFixNetwork": "The hub can't reach the configured endpoint. Is your provider running?",
+  "sysAiFixHttp": "The provider returned a non-2xx status. Verify the endpoint, model name, and API key.",
+  "sysAiFixEmptyResponse": "The provider answered with no content. Try a different model or rephrase the prompt.",
+  "channelSwitchOk": "Switched active channel to \"{name}\". Daemon restarted.",
+  "@channelSwitchOk": {
+    "placeholders": {
+      "name": {"type": "String"}
+    }
+  },
+  "channelSwitchFailed": "Channel switch failed: {detail}",
+  "@channelSwitchFailed": {
+    "placeholders": {
+      "detail": {"type": "String"}
+    }
+  },
+  "providerDescOllama": "Local `ollama serve`. Models stay on your machine. No API key needed.",
+  "providerDescOpenai": "OpenAI hosted API. Requires an API key. Data leaves your machine.",
+  "providerDescLmstudio": "Local LM Studio server. Models stay on your machine. No API key needed.",
+  "providerDescVllm": "Self-hosted vLLM or any other OpenAI-compatible server. Endpoint required.",
+  "providerDescCustom": "Anything else that speaks the OpenAI-compatible chat-completions wire (LiteLLM proxy, internal mirror, …).",
+  "welcomeDocLoadFailedBody": "Could not load the bundled doc \"{slug}\" ({locale}).\nTried: {attempted}\nUnderlying: {underlying}\nThis usually means the Studio build on disk predates the doc bundle. Rebuild Studio or open the online copy.",
+  "@welcomeDocLoadFailedBody": {
+    "placeholders": {
+      "slug": {"type": "String"},
+      "locale": {"type": "String"},
+      "attempted": {"type": "String"},
+      "underlying": {"type": "String"}
+    }
+  },
+  "hubUnreachableBanner": "Can't reach {endpoint} — open Settings",
+  "@hubUnreachableBanner": {
+    "placeholders": {
+      "endpoint": {"type": "String"}
+    }
+  },
+  "hubUnreachableOpenSettings": "Open Settings"
 }