Fix Dagger towncrier container using UTC instead of local time (#167)

## Summary
- The `build_changelog` Dagger container (`python:3.12-slim`) defaults to UTC, causing towncrier to stamp tomorrow's date when releases are cut in the evening PST.
- This is the root cause of the docs website (built via Dagger) showing Feb 12 while the repo CHANGELOG (built directly on the runner) correctly showed Feb 11.
- Fix: set `TZ=America/Los_Angeles` in the Dagger container before running towncrier.

## Verified
- `docker run --rm python:3.12-slim` → `towncrier _get_date()` returns `2026-02-12` (wrong)
- `docker run --rm -e TZ=America/Los_Angeles python:3.12-slim` → returns `2026-02-11` (correct)

## Test plan
- [ ] Merge, then trigger a build-blumeops release
- [ ] Verify the CHANGELOG date on https://docs.eblu.me/CHANGELOG matches the repo

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Reviewed-on: https://forge.ops.eblu.me/eblume/blumeops/pulls/167

.dagger/src/blumeops_ci/main.py

@@ -31,6 +31,7 @@ class BlumeopsCi:
         return await (
             dag.container()
             .from_("python:3.12-slim")
+            .with_env_variable("TZ", "America/Los_Angeles")
             # git is required because towncrier stages CHANGELOG.md via git add
             .with_exec(["apt-get", "update", "-qq"])
             .with_exec(["apt-get", "install", "-y", "-qq", "git"])

docs/changelog.d/fix-dagger-towncrier-tz.bugfix.md

@@ -0,0 +1 @@
+Set ``TZ=America/Los_Angeles`` in the Dagger ``build_changelog`` container so towncrier stamps the correct local date instead of UTC (which showed tomorrow's date for evening releases).