fix: Fix NAME cache IPv4/IPv6 key collisions and IPv6 SQLite overflow

[digrajpu]

The NAME cache was converting SOURCEIP to a plain integer before storing it as a SQLite key. This caused two bugs:

• Key collision: 0.0.0.1 and ::1 both produce integer 1, so they shared the same cache row and could overwrite each other's hostname.
• IPv6 failure: Most IPv6 addresses require 128 bits, exceeding SQLite's signed 64-bit integer limit, causing an OverflowError on write.

Fix: Replace the integer key with a family-tagged string (v4:192.0.2.2, v6:2001:db8::1) generated by ip_cache_key() using Python's ipaddress module. This guarantees no cross-family collisions and stores safely as a string in SQLite. Existing caches will cold-repopulate under the new key namespace; operators can use SC4S_CLEAR_NAME_CACHE=yes for a one-time cleanup on upgrade.

[Kawron]

@digrajpu please add description to this PR

[Kawron]

Code lgtm, but have you tested it manually? I think it will be worth doing to make sure we don't break anything