feat(backend): add Nakama OSS local base

[JOY (JOY)]

Summary

• accept Nakama OSS as the primary game-backend direction in ADR 0010
• add local Docker Compose setup for Nakama 3.38.0 + Postgres
• add a minimal TypeScript runtime module with secondspawn_health RPC
• update agent context and GitBook setup docs

Verification

• docker compose config
• docker compose up -d --build
• Nakama/Postgres containers healthy
• HTTP healthcheck returned 200
• authenticated device and called secondspawn_health RPC successfully
• Playwright opened Nakama Console at http://127.0.0.1:7351/#/login

Reviewer note

Draft PR because backend architecture changes still need independent reviewer pass before merge.

[gemini-code-assist]

Code Review

This pull request introduces Nakama OSS as the primary game backend, shifting Supabase to a supporting role for identity and administrative data. The implementation includes a Dockerized environment for Nakama and Postgres, a TypeScript runtime module with a health check RPC, and comprehensive documentation including ADR 0010. Feedback focuses on improving the TypeScript runtime entry point by using idiomatic function declarations and removing redundant code.

[gemini-code-assist]

Using a function declaration for InitModule is more idiomatic in Nakama TypeScript modules. This ensures the function is correctly hoisted and available in the global scope of the generated script, which is where the Nakama engine expects to find it.

Suggested change

	let InitModule: nkruntime.InitModule = function (
	ctx: nkruntime.Context,
	logger: nkruntime.Logger,
	nk: nkruntime.Nakama,
	initializer: nkruntime.Initializer
	) {
	initializer.registerRpc(rpcIdHealth, rpcHealth);
	logger.info("Second Spawn Nakama runtime loaded.");
	};
	function InitModule(
	ctx: nkruntime.Context,
	logger: nkruntime.Logger,
	nk: nkruntime.Nakama,
	initializer: nkruntime.Initializer
	) {
	initializer.registerRpc(rpcIdHealth, rpcHealth);
	logger.info("Second Spawn Nakama runtime loaded.");
	}

[gemini-code-assist]

The call to InitModule.bind(null) is redundant and has no effect. The bind method returns a new function without modifying the original, and since the return value is not assigned or used, this line is dead code and should be removed.

[JOY (JOY)]

Closing this draft as obsolete. The Nakama backend direction has since moved through dev with the current runtime layout and follow-up work in PR #8, while this older branch is conflicting and still contains the superseded scaffold shape.