build: add buildozer.spec for Android APK generation

Add buildozer configuration file for building Echo Chamber as an Android APK. This file configures:
- App metadata (name, version, package name)
- Android build settings (API 33, minAPI 21)
- Required permissions (Internet, storage)
- Build architecture (arm64-v8a, armeabi-v7a)

Force-added despite .gitignore since buildozer.spec is a configuration file that should be version controlled, unlike PyInstaller .spec files.

Author: claude

buildozer.spec

@@ -0,0 +1,94 @@
+[app]
+
+# (str) Title of your application
+title = Echo Chamber
+
+# (str) Package name
+package.name = echochamber
+
+# (str) Package domain (needed for android/ios packaging)
+package.domain = org.echochamber
+
+# (str) Source code where the main.py live
+source.dir = .
+
+# (list) Source files to include (let empty to include all the files)
+source.include_exts = py,png,jpg,kv,atlas,json
+
+# (str) Application versioning (method 1)
+version = 0.1.0
+
+# (list) Application requirements
+# comma separated e.g. requirements = sqlite3,kivy
+requirements = python3,kivy
+
+# (str) Custom source folders for requirements
+# Sets custom source for any requirements with recipes
+# requirements.source.kivy = ../../kivy
+
+# (list) Garden requirements
+#garden_requirements =
+
+# (str) Presplash of the application
+#presplash.filename = %(source.dir)s/data/presplash.png
+
+# (str) Icon of the application
+#icon.filename = %(source.dir)s/data/icon.png
+
+# (str) Supported orientation (landscape, sensorLandscape, portrait or all)
+orientation = portrait
+
+# (bool) Indicate if the application should be fullscreen or not
+fullscreen = 0
+
+# (list) Permissions
+android.permissions = INTERNET,WRITE_EXTERNAL_STORAGE,READ_EXTERNAL_STORAGE
+
+# (int) Target Android API, should be as high as possible.
+android.api = 33
+
+# (int) Minimum API your APK will support.
+android.minapi = 21
+
+# (str) Android NDK version to use
+android.ndk = 25b
+
+# (bool) Use --private data storage OR --dir public storage
+android.private_storage = True
+
+# (str) Android NDK directory (if empty, it will be automatically downloaded.)
+#android.ndk_path =
+
+# (str) Android SDK directory (if empty, it will be automatically downloaded.)
+#android.sdk_path =
+
+# (str) ANT directory (if empty, it will be automatically downloaded.)
+#android.ant_path =
+
+# (bool) If True, then skip trying to update the Android sdk
+# This can be useful to avoid excess Internet downloads or save time
+# when an update is due and you just want to test/build your package
+android.skip_update = False
+
+# (bool) If True, then automatically accept SDK license
+# agreements. This is intended for automation only. If set to False,
+# the default, you will be shown the license when first running
+# buildozer.
+android.accept_sdk_license = True
+
+# (str) The Android arch to build for, choices: armeabi-v7a, arm64-v8a, x86, x86_64
+android.archs = arm64-v8a,armeabi-v7a
+
+[buildozer]
+
+# (int) Log level (0 = error only, 1 = info, 2 = debug (with command output))
+log_level = 2
+
+# (int) Display warning if buildozer is run as root (0 = False, 1 = True)
+warn_on_root = 1
+
+# (str) Path to build artifact storage, absolute or relative to spec file
+build_dir = ./.buildozer
+
+# (str) Path to build output (i.e. .apk, .ipa) storage
+bin_dir = ./bin