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/services/imageCache.ts

@@ -3,6 +3,9 @@
 
 import { convertFileSrc } from "@tauri-apps/api/core";
 import { commands } from "$lib/api/bindings";
+import { createLogger } from "$lib/utils/logger";
+
+const log = createLogger("ImageCache");
 
 /**
  * Statistics about the thumbnail cache
@@ -48,7 +51,7 @@ export async function getCachedImageUrl(
       return convertFileSrc(cachedPath);
     }
   } catch (e) {
-    console.debug("Failed to check thumbnail cache:", e);
+    log.debug("Failed to check thumbnail cache:", e);
   }
 
   // Build server URL
@@ -63,7 +66,7 @@ export async function getCachedImageUrl(
   // Trigger background caching (fire and forget)
   commands.thumbnailSave(itemId, imageType, tag, serverImageUrl).catch((e) => {
     // Silently fail - caching is best-effort
-    console.debug("Background thumbnail cache failed:", e);
+    log.debug("Background thumbnail cache failed:", e);
   });
 
   // Return server URL for immediate display