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/playlist/AddToPlaylistModal.svelte

@@ -6,6 +6,9 @@
   import { toast } from "$lib/stores/toast";
   import CreatePlaylistModal from "./CreatePlaylistModal.svelte";
   import CachedImage from "$lib/components/common/CachedImage.svelte";
+  import { createLogger } from "$lib/utils/logger";
+
+  const log = createLogger("AddToPlaylist");
 
   interface Props {
     isOpen?: boolean;
@@ -39,7 +42,7 @@
         playlists = result.items;
       }
     } catch (e) {
-      console.error("[AddToPlaylist] Failed to load playlists:", e);
+      log.error("Failed to load playlists:", e);
       toast.error("Failed to load playlists");
     } finally {
       loading = false;
@@ -54,7 +57,7 @@
       toast.success(`Added to "${playlist.name}"`);
       onClose?.();
     } catch (e) {
-      console.error("[AddToPlaylist] Failed to add:", e);
+      log.error("Failed to add:", e);
       toast.error("Failed to add to playlist");
     } finally {
       adding = null;

src/lib/components/playlist/CreatePlaylistModal.svelte

@@ -2,6 +2,9 @@
   import { goto } from "$app/navigation";
   import { auth } from "$lib/stores/auth";
   import { toast } from "$lib/stores/toast";
+  import { createLogger } from "$lib/utils/logger";
+
+  const log = createLogger("CreatePlaylist");
 
   interface Props {
     isOpen?: boolean;
@@ -27,7 +30,7 @@
       onClose?.();
       goto(`/library/${result.id}`);
     } catch (e) {
-      console.error("[CreatePlaylist] Failed:", e);
+      log.error("Failed:", e);
       toast.error("Failed to create playlist");
     } finally {
       creating = false;