connections.cgi: Enhance with zone filter and search functionality

connections.cgi: Enhance with zone filter and search functionality

Improved connections.cgi with the following features:
- Added zone filter to select network zones (LAN, INTERNET, DMZ, etc.) via clickable legend.
- Included NAT IPs in filtering for all zones.
- Added search function to filter connections by IP, port, or protocol. With jQuery toggle on/off .
- Display filter status showing active filters and connection count.

FIXES/extensions:
- Fix multi-pattern search to use AND logic

- Corrected search filter to apply AND instead of OR for IP, port, and protocol criteria.
- Added case-insensitive protocol matching and input sanitization for robustness.
- Added ipcolour cache and pre-filtered networks.
- Replaced external sort with Perl sorting for conntrack table.
- Removed redundant close(CONNTRACK) call.

Signed-off-by: ummeegge <ummeegge@ipfire.org>