chore: gitignore local Dolt dev clones (dolt-data/)

Local dev uses a Dolt clone of post-no-preference/earnings under dolt-data/
(git-ignored). Production keeps clones in DOLT_DATA_DIR outside the repo tree —
the deploy is rsync --delete of the tree, so a clone inside it would be unsafe.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.gitignore

@@ -39,6 +39,10 @@ alembic/versions/__pycache__/
 # Generated SSL bundle
 combined-ca-bundle.pem
 
+# Dolt local dev clones. Production keeps clones in DOLT_DATA_DIR OUTSIDE the
+# repo tree (deploy is rsync --delete of the tree); this dir is dev-only.
+dolt-data/
+
 # Local research artifacts
 # Backtest reports in reports/ are tracked: they are the evidence behind the
 # production baseline in the README. The snapshot DBs they run against are not.