generate_bird_config() creates /etc/bird/route-tables.conf with
protocol kernel blocks for each per-list routing table, tagged with
BGP community (AS:table_num). Each kernel syncer gets its own BIRD
table with a pipe to master4/master6. Uses 'learn' to import routes
from external programs. Only runs if birdc is installed.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>