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/routes/library/favorites/+page.svelte

@@ -29,6 +29,9 @@
     favoritesRouteUrl,
     emptyStateMessage,
   } from "$lib/utils/favoritesView";
+  import { createLogger } from "$lib/utils/logger";
+
+  const log = createLogger("FavoritesPage");
 
   const scope = $derived(resolveFavoritesScope($page.url.searchParams.get("scope")));
 
@@ -49,7 +52,7 @@
       const result = await repo.getFavorites(currentScope, { limit: 500 });
       items = result.items;
     } catch (error) {
-      console.error("Failed to load favorites:", error);
+      log.error("Failed to load favorites:", error);
       loadError = "Could not load your favourites.";
       items = [];
     } finally {