feat: offline flavor without sync or network access (#39)

README.md

@@ -119,9 +119,21 @@ APK and a `.sha256` checksum attached — the same APK the F-Droid repository
 serves. For automatic updates from there, use
 **[Obtainium](https://github.com/ImranR98/Obtainium)** and
 **[add Agendula in one tap](https://apps.obtainium.imranr.dev/redirect?r=obtainium://add/https://codeberg.org/jlmakiola/agendula)**.
+Each release carries two APKs (see [Offline version](#offline-version)), so set
+*Filter APKs by regular expression* to `^agendula_v` to always get the regular
+app.
 Betas of upcoming versions are published there too, as pre-releases; to test
 them, switch on *Include prereleases* for Agendula in Obtainium.
 
+### Offline version
+
+Each Codeberg release also carries `agendula-offline_v<version>.apk`: Agendula
+without CalDAV sync and **without the network permission**, so it cannot
+connect to anything. It installs alongside the regular app rather than replacing
+it; move tasks between the two with Settings → Storage → Export / Import. In
+Obtainium, pick it with *Filter APKs by regular expression* set to
+`^agendula-offline_v`.
+
 ### Build from source
 
 ```sh