feat: add subscription search/sort, rewrite README, upgrade infrastructure

- Subscription list: search by name (case-insensitive), sort by latest
  update / name A-Z / name Z-A / unread count, preference persisted
- README: add build instructions, changelog, reorganize sections
- Upgrade Flutter SDK, Gradle/AGP/Kotlin, migrate to Dart null safety
- Bundle built-in font assets (OpenSans/Roboto/SourceSerif)
- Rename Android package to icu.cytrogen.fluent_reader
- Add i18n strings for sort/search across all 9 locales

Merge pull request #108 from yang991178/1.0.4

1.0.4

Merge branch 'master' of https://github.com/mustafagenc/fluent-reader-lite into 1.0.4

update dependencies

Turkish language support added

Merge pull request #68 from yang991178/1.0.3

Version 1.0.3

add multiple locales

add german language support

update localizations

add error messages

turn off autocorrect by default

add google reader api support

add inoreader support

add customizable text scale

use jaguar to serve resources

add feedbin support

initial commit