Move backend files to root level for cleaner GitHub display

- Move all backend files from swingmusic/ to root level
- Backend files now display directly on GitHub repository page
- Keep client applications as submodules (swingmusic-android, swingmusic-desktop, swingmusic-webclient)
- Update README to reflect new structure (no cd swingmusic needed)
- Cleaner, more professional GitHub repository layout

Files moved to root:
- src/ (main source code)
- pyproject.toml, requirements.txt, run.py
- swingmusic.spec, uv.lock, version.txt
- services/

Result: GitHub shows backend files directly while maintaining organized structure

src/swingmusic/enums/album_versions.py

@@ -0,0 +1,67 @@
+from enum import Enum
+
+
+class AlbumVersionEnum(Enum):
+    """
+    Enum that registers supported album versions.
+    """
+
+    Explicit = ("explicit",)
+    _360_AUDIO = ("360 audio",)
+
+    ANNIVERSARY_EDITION = ("anniversary",)
+    DIAMOND_EDITION = ("diamond",)
+    Centennial_EDITION = ("centennial",)
+    GOLDEN_EDITION = ("gold",)
+    PLATINUM_EDITION = ("platinum",)
+    SILVER_EDITION = ("silver",)
+    ULTIMATE_EDITION = ("ultimate",)
+
+    EXPANDED = ("expanded",)
+    EXTENDED = ("extended",)
+
+    DELUXE = ("deluxe",)
+    SUPER_DELUXE = ("super deluxe",)
+    COMPLETE = ("complete",)
+
+    LEGACY_EDITION = ("legacy",)
+    SPECIAL_EDITION = ("special",)
+    COLLECTORS_EDITION = ("collector",)
+    ARCHIVE_EDITION = ("archive",)
+
+    Acoustic = ("acoustic",)
+    instrumental = ("instrumental",)
+    DOUBLE_DISC = ("double disc", "double disk")
+    Unplugged = ("unplugged",)
+
+    SUMMER_EDITION = ("summer",)
+    WINTER_EDITION = ("winter",)
+    SPRING_EDITION = ("spring",)
+    FALL_EDITION = ("fall",)
+
+    BONUS_EDITION = ("bonus",)
+    BONUS_TRACK = ("bonus track",)
+
+    ORIGINAL = ("original", " og ", "og ")
+    INTL_VERSION = ("international",)
+    UK_VERSION = ("uk version",)
+    US_VERSION = ("us version",)
+    PARENTAL_ADVISORY = ("PA version",)
+
+    Limited_EDITION = ("limited",)
+
+    MONO = ("mono",)
+    STEREO = ("stereo",)
+
+    HI_RES = ("Hi-Res",)
+    RE_MIX = ("re-mix",)
+    RE_RECORDED = ("re-recorded", "rerecorded")
+    REISSUE = ("reissue",)
+    REMASTERED = ("remaster",)
+
+
+def get_all_keywords():
+    """
+    Returns a joint string of all album versions.
+    """
+    return "|".join("|".join(i.value) for i in AlbumVersionEnum)