feat: add durable allocator claim boundary

server/migrations/0004_allocator_registry.sql

@@ -0,0 +1,29 @@
+-- Durable allocator registry. Agones remains the provider-facing lifecycle
+-- authority; these rows are the control-plane's auditable claim projection.
+CREATE TABLE game_servers (
+    server_id TEXT PRIMARY KEY,
+    region TEXT NOT NULL CHECK (region IN ('EU', 'NA')),
+    build TEXT NOT NULL,
+    protocol_version INTEGER NOT NULL CHECK (protocol_version > 0),
+    transport TEXT NOT NULL CHECK (transport IN ('enet', 'steam_sdr')),
+    state TEXT NOT NULL CHECK (state IN ('READY', 'ALLOCATED')),
+    updated_at TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+
+CREATE TABLE allocations (
+    allocation_id TEXT PRIMARY KEY,
+    match_id TEXT NOT NULL UNIQUE,
+    server_id TEXT NOT NULL REFERENCES game_servers(server_id),
+    region TEXT NOT NULL CHECK (region IN ('EU', 'NA')),
+    build TEXT NOT NULL,
+    protocol_version INTEGER NOT NULL CHECK (protocol_version > 0),
+    transport TEXT NOT NULL CHECK (transport IN ('enet', 'steam_sdr')),
+    request_digest BYTEA NOT NULL,
+    state TEXT NOT NULL CHECK (state = 'ALLOCATED'),
+    allocated_at TIMESTAMPTZ NOT NULL,
+    created_at TIMESTAMPTZ NOT NULL DEFAULT now()
+);
+
+CREATE INDEX game_servers_ready_compatibility
+    ON game_servers (region, build, protocol_version, transport, server_id)
+    WHERE state = 'READY';