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/lib/components/library/DownloadButton.svelte

@@ -1,7 +1,6 @@
 <script lang="ts">
   import { downloads } from "$lib/stores/downloads";
   import { auth } from "$lib/stores/auth";
-  import { invoke } from "@tauri-apps/api/core";
   import { commands } from "$lib/api/bindings";
   import DownloadButtonCore from "./DownloadButtonCore.svelte";
   import type { DownloadState } from "./DownloadButtonCore.svelte";
@@ -81,7 +80,7 @@
           }
 
           // Get target directory
-          const targetDir = await invoke<string>("storage_get_path");
+          const targetDir = await commands.storageGetPath();
           console.log("   Target directory:", targetDir);
 
           // Queue and start download in single atomic operation