refactor(logging): route frontend console calls through the logger

TRACES: | DR-204

484 ungated `console.*` calls across 63 non-test frontend files shipped to
end users with no way to turn them off. Mechanical substitution, no control
flow, error handling or message semantics changed:

  console.log / console.debug -> log.debug
  console.info                -> log.info
  console.warn                -> log.warn
  console.error               -> log.error

Hand-written `"[Scope] …"` prefixes are dropped where the logger's scope
now carries them; scope names that already existed are preserved verbatim
(`[Auth]`, `[VideoPlayer]`, `[PiP]`, …) and inferred from the filename
where a file had none. `src/routes/player/[id]/+page.svelte` keeps its
`NextEpisode` and `AutoPlay` sub-scopes as separate loggers rather than
flattening them into the page scope.

`grep -rn 'console\.' src/` now matches nothing outside the tests and the
facade itself.

src/lib/components/library/SeriesDownloadButton.svelte

@@ -3,6 +3,9 @@
   import { auth } from "$lib/stores/auth";
   import { commands } from "$lib/api/bindings";
   import { QUALITY_PRESETS, type QualityPreset } from "$lib/api/quality-presets";
+  import { createLogger } from "$lib/utils/logger";
+
+  const log = createLogger("SeriesDownloadButton");
 
   interface Props {
     seriesId: string;
@@ -40,11 +43,11 @@
     try {
       const userId = $auth.user?.id;
       if (!userId) {
-        console.error("No user ID found");
+        log.error("No user ID found");
         return;
       }
 
-      console.log("📺 Starting series download for:", seriesName, "quality:", quality);
+      log.debug("📺 Starting series download for:", seriesName, "quality:", quality);
 
       // Get target directory
       const targetDir = await commands.storageGetPath();
@@ -59,7 +62,7 @@
         quality
       );
 
-      console.log(`   Queued ${downloadIds.length} episodes for download`);
+      log.debug(`   Queued ${downloadIds.length} episodes for download`);
 
       // Pin the series item
       await downloads.pinItem(seriesId);
@@ -69,9 +72,9 @@
       // rest as slots free up.
       const handle = auth.getRepository().getHandle();
       await commands.enqueueVideoDownloads(handle, downloadIds, targetDir);
-      console.log("   Episodes enqueued; backend pump will start them");
+      log.debug("   Episodes enqueued; backend pump will start them");
     } catch (error) {
-      console.error("Failed to start series download:", error);
+      log.error("Failed to start series download:", error);
     } finally {
       isProcessing = false;
     }