feat(combos): default-enable vision/audio adapter with mimo fallback

- Enable vision + audioInput capacity-adapter pools by default for new
  and existing users (mergeWithDefaults backward-compat)
- Fall back to oc/mimo-v2.5-free when an enabled pool has no models
  configured, both in the backend resolver and the combos UI (auto
  refill on removing the last model from a pool)
- Hide PDF/Video from the Vision Adapter UI (PDF never implemented,
  Video lacks translator support) while keeping the settings shape
- Exclude combos from the model picker when opened from the Vision
  Adapter section
- mimo-v2.5 registry entry now declares audioInput/videoInput
- Simplify combo strategy and Vision Adapter descriptions

src/lib/db/repos/settingsRepo.js

@@ -17,7 +17,14 @@ const DEFAULT_SETTINGS = {
   comboStrategy: "fallback",
   comboStickyRoundRobinLimit: 1,
   comboStrategies: {},
+  capacityAdapter: {
+    vision: { enabled: true, roundRobin: false, models: [] },
+    pdf: { enabled: false, roundRobin: false, models: [] },
+    audioInput: { enabled: true, roundRobin: false, models: [] },
+    videoInput: { enabled: false, roundRobin: false, models: [] },
+  },
   requireLogin: true,
+  requireApiKey: true,
   tunnelDashboardAccess: true,
   authMode: "password",
   oidcIssuerUrl: "",