refactor(domain): flatten shared/media package into single module

Six small files (audio, video, subtitle, info, matching, tracks_mixin
+ __init__) collapsed into one ~250 LoC media.py module. Python treats
media.py and media/__init__.py interchangeably, so the 12 import sites
that read 'from alfred.domain.shared.media import ...' continue to work
without changes.

Reasoning: the whole bounded context fits on one screen; splitting into
sub-modules added more navigation friction than it saved. Tests stay
green (1077 passed).

CHANGELOG.md

@@ -57,6 +57,14 @@ callers).
 
 ### Internal
 
+- **Flattened `alfred.domain.shared.media/` package into a single
+  `media.py` module.** The 6-file package (audio, video, subtitle,
+  info, matching, tracks_mixin + `__init__`) collapsed into one ~250
+  LoC module. All 12 import sites continue to resolve unchanged
+  (`from alfred.domain.shared.media import AudioTrack, MediaInfo, …`)
+  since Python treats `media.py` and `media/__init__.py`
+  interchangeably for import paths. Easier to scan when the whole
+  bounded-context fits on one screen.
 - **`SubtitleKnowledgeBase` types `language_registry` against the
   `LanguageRepository` port** instead of the concrete `LanguageRegistry`
   class. The default constructor still instantiates the concrete adapter