The README had nothing on any of the three, leaving an operator with
no answer to which files to back up, whether a hot copy is safe, how
to restore, or what a newer image does to their data.
Adds a "Backup, Restore, and Upgrades" section covering:
- the backup set: webhooker.db, one events-{uuid}.db per webhook, one
archive-{uuid}.db per webhook with a database target, all under
DATA_DIR, plus the .env that is not under it
- why a hot copy is unsafe (no journal_mode pragma is issued on any
DSN, so every database runs the default rollback journal, and the
main and event handles stay open for the process lifetime), with
stop-copy-start and sqlite3 .backup as the safe procedures
- restore: the whole set together, since a missing events DB is
created empty rather than erroring, and chown to UID 1000 because
SQLite needs to write the journal beside the database
- upgrade: AutoMigrate runs unconditionally on every start against
all three database kinds, there is no schema version table and no
down migrations, so back up first and downgrade is unsupported
- that event and archive databases hold full payload bodies and
headers, that event databases also carry target credentials until
#206 is fixed, and that target config in webhooker.db is
unencrypted, tracked in #212
Docs only; no code, config, script or build changes.
