Migrate all IPC call sites to typed tauri-specta commands.*

Replace the remaining ~155 untyped invoke() calls across stores, services,
components, and routes with the generated commands.* wrappers from
$lib/api/bindings, so every IPC call is compile-time-checked against the
command signatures.

- Register repository_get_subtitle_url and repository_get_video_download_url
  in specta_builder() and the invoke_handler; regenerate bindings.ts.
- Source duplicated wire types (AutoplaySettings, CacheConfig, Session,
  ConnectivityStatus, audio/video settings, etc.) from bindings.
- Fix two bugs surfaced by the typed wrappers:
  - VideoDownloadButton passed an un-awaited Promise as the stream URL.
  - setAutoplaySettings omitted the required userId argument.
- Update unit tests asserting the old invoke(name, args) shape.
- Remove the five param-naming guard tests; the compiler and codegen now
  enforce what they checked.

svelte-check: 0 errors. vitest: green. cargo test --lib: green.

src/routes/+layout.svelte

@@ -3,7 +3,6 @@
   import { page } from "$app/stores";
   import { goto } from "$app/navigation";
   import { platform } from "@tauri-apps/plugin-os";
-  import { invoke } from "@tauri-apps/api/core";
   import "../app.css";
   import { auth, needsReauth, isAuthenticated } from "$lib/stores/auth";
   import { connectivity, isConnected } from "$lib/stores/connectivity";