Rename the project to ihasvpn

WGX shares its name with several other WireGuard tools, so the project
becomes ihasvpn, alongside ihasmail.

- Module github.com/Coffey-Labs/ihasvpn, command cmd/ihasvpn, image
  ghcr.io/coffey-labs/ihasvpn.
- Environment variables move from WGX_* to IHASVPN_*. The default database
  is ihasvpn.db, the nftables table is `ihasvpn`, metrics are ihasvpn_*, and
  the session cookie and theme key are renamed, so existing sessions end.
- The mark is the ihasmail cat peeking over the edge of a shield, drawn as
  a vector. docs/brand/generate.py builds the mark, mono mark, wordmarks,
  social card, favicons and app icons from that one drawing.
- The console takes ihasmail's palette: the ihasmail.org teal-navy for dark,
  its contrast-checked light tiers with the site's light accent, received
  traffic in the cat's orange and sent in teal. The wordmark weight and
  font stack follow ihasmail.org.
- Detail values wrap at spaces before breaking inside an address, so an
  IPv6 tunnel address no longer splits mid-number.
- The README history note about the earlier WGX installer is gone with the
  name it explained. Screenshots retaken.

internal/netcfg/nft.go

@@ -12,7 +12,7 @@ import (
 	"strings"
 )
 
-// Rules describes the firewall WGX wants.
+// Rules describes the firewall ihasvpn wants.
 type Rules struct {
 	// Iface is the WireGuard interface name, e.g. wg0.
 	Iface string
@@ -31,7 +31,7 @@ type Rules struct {
 	// "the VPN connects but websites hang".
 	ClampMSS bool
 	// Table names the nftables table, so a host with its own rules never
-	// collides with ours. Defaults to "wgx".
+	// collides with ours. Defaults to "ihasvpn".
 	Table string
 }
 
@@ -40,7 +40,7 @@ type Rules struct {
 func Ruleset(r Rules) string {
 	table := r.Table
 	if table == "" {
-		table = "wgx"
+		table = "ihasvpn"
 	}
 	var b strings.Builder
 	fmt.Fprintf(&b, "table inet %s\n", table)
@@ -88,10 +88,10 @@ func Apply(ctx context.Context, r Rules) error {
 	return runNFT(ctx, Ruleset(r))
 }
 
-// Remove deletes the WGX table, ignoring the case where it is already gone.
+// Remove deletes the ihasvpn table, ignoring the case where it is already gone.
 func Remove(ctx context.Context, table string) error {
 	if table == "" {
-		table = "wgx"
+		table = "ihasvpn"
 	}
 	script := fmt.Sprintf("table inet %s\ndelete table inet %s\n", table, table)
 	return runNFT(ctx, script)