feat(lol/v-migration): Zig gateway replaces vweb V gateway

Estate-wide V-lang ban (2026-04-10). New lol/api/zig-gateway/ (Zig 0.15.2)
replaces lol/api/v-gateway/:

- Serves REST, gRPC, and GraphQL simultaneously on three ports (base,
  base+1, base+2); REST is the primary, gRPC and GraphQL run as detached
  threads
- Reads corpus from data_dir/languages/*.json via Dir.iterate(); supports
  language lookup by ISO 639-3 code
- All domain types (LanguageInfo, CrawlStatus, CorpusStats) parsed from
  JSON via std.json.parseFromSlice
- Port configurable via LOL_GATEWAY_PORT (default 9100)

The V gateway in lol/api/v-gateway/ is retained as reference; remove
once the Zig binary is confirmed healthy in staging.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: hyperpolymath

lol/api/zig-gateway/build.zig

@@ -0,0 +1,36 @@
+// SPDX-License-Identifier: PMPL-1.0-or-later
+// Copyright (c) 2026 Jonathan D.A. Jewell (hyperpolymath) <j.d.a.jewell@open.ac.uk>
+//
+// Build configuration for LOL (1000Langs) Zig API gateway.
+// Replaces the V vweb gateway in api/v-gateway/.
+// Requires Zig 0.15.2+.
+
+const std = @import("std");
+
+pub fn build(b: *std.Build) void {
+    const target   = b.standardTargetOptions(.{});
+    const optimize = b.standardOptimizeOption(.{});
+
+    const main_mod = b.createModule(.{
+        .root_source_file = b.path("src/main.zig"),
+        .target           = target,
+        .optimize         = optimize,
+    });
+
+    const exe = b.addExecutable(.{
+        .name        = "lol_gateway",
+        .root_module = main_mod,
+    });
+    b.installArtifact(exe);
+
+    const run_cmd = b.addRunArtifact(exe);
+    run_cmd.step.dependOn(b.getInstallStep());
+    if (b.args) |args| run_cmd.addArgs(args);
+    const run_step = b.step("run", "Run the LOL API gateway");
+    run_step.dependOn(&run_cmd.step);
+
+    const unit_tests = b.addTest(.{ .root_module = main_mod });
+    const run_tests  = b.addRunArtifact(unit_tests);
+    const test_step  = b.step("test", "Run unit tests");
+    test_step.dependOn(&run_tests.step);
+}