chore: prep 2.1.0a1 alpha release with procrastinate support

Bumps version to a PEP 440 alpha so the procrastinate integration can
ship for early users without committing to it as a stable 2.1.0.

Also drops the `--format "{base}"` from the release workflow's dunamai
call. `{base}` strips the pre-release suffix, which broke two things:
the tag/version equality check (`v2.1.0a1` != `v2.1.0`) and the artifact
upload path (built wheels are named `taskbadger-2.1.0a1-*`, not
`taskbadger-2.1.0-*`). The default dunamai output is already PEP 440,
so this fix is general — beta/rc tags will also work going forward.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: snopoke

.github/workflows/release.yml

@@ -40,7 +40,7 @@ jobs:
           enable-cache: true
       - name: Add version to environment vars
         run: |
-          PROJECT_VERSION=$(uvx dunamai from any --format "{base}")
+          PROJECT_VERSION=$(uvx dunamai from any)
           echo "PROJECT_VERSION=$PROJECT_VERSION" >> $GITHUB_ENV
       - name: Check if tag version matches project version
         run: |

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "taskbadger"
-version = "2.0.0"
+version = "2.1.0a1"
 description = "The official Python SDK for Task Badger"
 requires-python = ">=3.10"
 authors = []