feat: import Jaromail sieve rules

[jaromil]

Summary

• add jaro sieve-import FILE for importing Jaromail-generated Sieve files into Filters.txt, Aliases.txt, whitelist.abook, and blacklist.abook
• make Sieve import idempotent and preserve generated/system Sieve rules as non-user state
• fix filter cache scope so imported filters regenerate into Filters.sieve
• expose sieve and sieve-import in help and shell completions
• add a focused Sieve import regression test and run it in PR CI

Tests

• make
• extras/test/run-source.sh
• extras/test/test-addressbook-parse.sh
• extras/test/test-filtering.sh
• extras/test/test-sieve-import.sh
• extras/test/test-helpers.sh

Note: .gestalt/ and the local example jaromil.sieve are intentionally untracked and not included.