chore: rename project from gosearch to kafka

A search engine named after a man who proved answers don't exist.

Renamed everywhere user-facing:
- Brand name, UI titles, OpenSearch description, CSS filename
- Docker service name, NixOS module (services.kafka)
- Cache key prefix (kafka:), User-Agent strings (kafka/0.1)
- README, config.example.toml, flake.nix descriptions

Kept unchanged (internal):
- Go module path: github.com/ashie/gosearch
- Git repository URL: git.ashisgreat.xyz/penal-colony/gosearch
- Binary entrypoint: cmd/searxng-go

flake.nix

@@ -1,5 +1,5 @@
 {
-  description = "gosearch — privacy-respecting, open metasearch engine";
+  description = "kafka — privacy-respecting, open metasearch engine";
 
   inputs = {
     nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
@@ -17,7 +17,7 @@
         in
         {
           default = pkgs.buildGoModule {
-            pname = "gosearch";
+            pname = "kafka";
             version = "0.1.0";
             src = ./.;
 
@@ -32,7 +32,7 @@
 
             meta = with pkgs.lib; {
               description = "Privacy-respecting, open metasearch engine";
-              homepage = "https://git.ashisgreat.xyz/penal-colony/gosearch";
+              homepage = "https://git.ashisgreat.xyz/penal-colony/kafka";
               license = licenses.mit;
               platforms = platforms.linux ++ platforms.darwin;
             };
@@ -41,16 +41,16 @@
 
       nixosModules.default = { config, lib, pkgs, ... }:
         let
-          cfg = config.services.gosearch;
+          cfg = config.services.kafka;
         in
         {
-          options.services.gosearch = {
-            enable = lib.mkEnableOption "gosearch metasearch engine";
+          options.services.kafka = {
+            enable = lib.mkEnableOption "kafka metasearch engine";
 
             package = lib.mkOption {
               type = lib.types.package;
               default = self.packages.${pkgs.system}.default;
-              description = "gosearch package to use.";
+              description = "kafka package to use.";
             };
 
             port = lib.mkOption {
@@ -73,41 +73,41 @@
 
             config = lib.mkOption {
               type = lib.types.path;
-              default = "/etc/gosearch/config.toml";
+              default = "/etc/kafka/config.toml";
               description = "Path to config.toml file.";
             };
 
             user = lib.mkOption {
               type = lib.types.str;
-              default = "gosearch";
+              default = "kafka";
               description = "System user to run as.";
             };
 
             group = lib.mkOption {
               type = lib.types.str;
-              default = "gosearch";
+              default = "kafka";
               description = "System group to run as.";
             };
 
             stateDir = lib.mkOption {
               type = lib.types.path;
-              default = "/var/lib/gosearch";
+              default = "/var/lib/kafka";
               description = "State directory.";
             };
           };
 
           config = lib.mkIf cfg.enable {
-            users.users.${cfg.user} = lib.mkIf (cfg.user == "gosearch") {
+            users.users.${cfg.user} = lib.mkIf (cfg.user == "kafka") {
               isSystemUser = true;
               group = cfg.group;
               home = cfg.stateDir;
               createHome = true;
             };
 
-            users.groups.${cfg.group} = lib.mkIf (cfg.group == "gosearch") { };
+            users.groups.${cfg.group} = lib.mkIf (cfg.group == "kafka") { };
 
-            systemd.services.gosearch = {
-              description = "gosearch metasearch engine";
+            systemd.services.kafka = {
+              description = "kafka metasearch engine";
               after = [ "network.target" ];
               wantedBy = [ "multi-user.target" ];