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/+page.svelte

@@ -14,6 +14,9 @@
   import { assumedLibraryRatio } from "$lib/components/library/libraryMosaic";
   import { useScrollRestore } from "$lib/utils/scrollContainer";
   import type { MediaItem, Library } from "$lib/api/types";
+  import { createLogger } from "$lib/utils/logger";
+
+  const log = createLogger("HomePage");
 
   // Home scrolls in its own box rather than the shell's, and is destroyed on
   // every navigation away — so its offsets live in the module-level memory,
@@ -40,7 +43,7 @@
       const platformName = await platform();
       isAndroid = platformName === "android";
     } catch (err) {
-      console.error("Platform detection failed:", err);
+      log.error("Platform detection failed:", err);
     }
 
     if ($isAuthenticated) {