Move to the 1.1 series, from one place rather than three

The series a build is named for was written out three times — in the
build file and in both workflows' tag lines — so bumping it meant
changing all three and a release could be tagged one thing and built as
another. It now lives in gradle.properties as plgVersionSeries, which
the build reads when it stamps the APK and both workflows read when they
name the tag.

Set to 1.1.

versionCode is deliberately left as the CI run number alone, which is
what makes the bump safe: the run number keeps climbing across a change
of series, so 1.1 never looks like a downgrade to Android and an OTA
update is not interrupted. The series is a name for people; the run
number is what the machines compare. The updater already read only the
trailing number, and its comments now say so rather than naming 1.0.

Co-Authored-By: Claude Opus 5 <[email protected]>
Claude-Session: https://claude.ai/code/session_019Pr6B8xDDtJJcb6WJMw7Ud

CLAUDE.md

@@ -46,7 +46,7 @@ Skipping step 4 leaves a branch whose head was never built and no release.
 Both long-lived branches publish, so a merge is a release, not just an
 integration:
 
-- **`dev`** → `ci.yml` publishes a `v1.0.N-dev` **prerelease**, offered by the
+- **`dev`** → `ci.yml` publishes a `v<series>.N-dev` **prerelease**, offered by the
   in-app updater to anyone on the Dev channel.
 - **`main`** → `release.yml` publishes a **production** release, which the
   updater installs for everyone on the Production channel.