list_filter_rules silently dropped stored rules that failed to re-parse,
making a rule disappear from enforcement with no trace. Now each
unparseable row is WARN-logged with its rule id and skipped, so the
failure is visible instead of indistinguishable from "never uploaded".
Also stop nunciod's boot-time filter load from collapsing a genuine
database error into an empty rule set: load_initial_filter_rules
propagates the error (ERROR-logged) instead of unwrap_or_default(),
so a DB failure fails startup visibly rather than quietly disabling
all filtering.
Refs #247