Preserve connect block order on rehash

[eaescob]

Summary

This updates merge_connects() so /rehash rebuilds the active connect list in the order the connect {} blocks appear in the configuration file.

Previously, a fresh startup effectively restored config order because new_connects was built by head insertion and then inserted into connects by head insertion again. During /rehash, however, existing named connect blocks were updated in place, so reordering unchanged connect {} blocks in the config did not affect the active connect list until restart.

The active connect list matters for autoconnect behavior: try_connections() scans connects from the head and attempts only the first eligible uplink during a pass, then rotates that attempted entry to the end.

Changes

• Reverse the parsed new_connects list before merging so it is processed in config-file order.
• Detach and reuse matching existing aConnect objects so active references are preserved.
• Keep removed but still referenced connect blocks as expired entries at the end of the list.
• Preserve duplicate-name collapse behavior.

Validation

• git diff --check
• Built on eescobar@irc with autoreconf -vfi, ./configure --prefix=$HOME/dalnet/ircd, and make -j$(nproc).
• Ran a contained test daemon on localhost, reordered two connect {} blocks, issued /rehash, and confirmed /stats c changed from uplink-a, uplink-b to uplink-b, uplink-a without restart.