chore(repo): stop tracking build artifacts; add README, license metadata, ruff config

Untrack iso/out/ (3.4 GB ISO), packaging/*/pkg/ trees, *.pkg.tar.zst and
tanin-icons/src/ (529 files) and ignore them going forward. Files stay on
disk. NOTE: history still carries ~13 GiB of old ISO blobs — needs a
git filter-repo pass (see README/report).

Also: first README.md, license + license-files in pyproject, minimal ruff
config, demo scripts moved to scripts/demo/.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

pyproject.toml

@@ -2,6 +2,8 @@
 name = "taninux"
 version = "0.2.0"
 description = "TANINUX — central Linux maintenance & management TUI for Arch. Pillars: maintain, update, kernel, suggest, health."
+license = "GPL-3.0-or-later"
+license-files = ["LICENSE"]
 requires-python = ">=3.11"
 dependencies = [
     "textual>=0.86",
@@ -20,6 +22,8 @@ taninux = "taninux.cli:main"
 taninux-gtk = "taninux.gui.app:main"
 tsettings = "taninux.gui.app:main_settings"
 thub = "taninux.gui.app:main_hub"
+tmusic = "taninux.music.app:main"
+tfiles = "taninux.files.app:main"
 
 [build-system]
 requires = ["hatchling"]
@@ -27,3 +31,11 @@ build-backend = "hatchling.build"
 
 [tool.hatch.build.targets.wheel]
 packages = ["src/taninux"]
+
+[tool.ruff]
+line-length = 100
+target-version = "py311"
+
+[tool.ruff.lint]
+select = ["E", "F", "W", "B", "UP", "BLE"]
+ignore = ["E501"]