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/DownloadButton.svelte

@@ -4,6 +4,9 @@
   import { commands } from "$lib/api/bindings";
   import DownloadButtonCore from "./DownloadButtonCore.svelte";
   import type { DownloadState } from "./DownloadButtonCore.svelte";
+  import { createLogger } from "$lib/utils/logger";
+
+  const log = createLogger("DownloadButton");
 
   /**
    * Single audio track download button
@@ -39,7 +42,7 @@
   });
 
   async function handleClick() {
-    console.log("🖱️ Download button clicked! Current status:", status);
+    log.debug("🖱️ Download button clicked! Current status:", status);
     if (isProcessing) return;
 
     isProcessing = true;
@@ -63,25 +66,25 @@
         // Start download
         const userId = $auth.user?.id;
         if (!userId) {
-          console.error("No user ID found");
+          log.error("No user ID found");
           return;
         }
 
         try {
           const repo = auth.getRepository();
 
-          console.log("🎯 Starting download for item:", itemId);
+          log.debug("🎯 Starting download for item:", itemId);
 
           // Get stream URL
           const streamUrl = await repo.getAudioStreamUrl(itemId);
-          console.log("   Stream URL obtained:", streamUrl?.substring(0, 50) + "...");
+          log.debug("   Stream URL obtained:", streamUrl?.substring(0, 50) + "...");
           if (!streamUrl) {
             throw new Error("Failed to get stream URL");
           }
 
           // Get target directory
           const targetDir = await commands.storageGetPath();
-          console.log("   Target directory:", targetDir);
+          log.debug("   Target directory:", targetDir);
 
           // Queue and start download in single atomic operation
           const downloadId = await commands.downloadItemAndStart({
@@ -93,16 +96,16 @@
             artistName: artistName || null,
             albumName: albumName || null,
           });
-          console.log("   Download queued and started with ID:", downloadId);
+          log.debug("   Download queued and started with ID:", downloadId);
 
           // Refresh downloads list
           await downloads.refresh(userId);
         } catch (e) {
-          console.error("❌ Failed to start download:", e);
+          log.error("❌ Failed to start download:", e);
         }
       }
     } catch (error) {
-      console.error("Download operation failed:", error);
+      log.error("Download operation failed:", error);
     } finally {
       isProcessing = false;
     }