feat(meditate): Meditate's server, its sealed tables, and SimpleLogin's way back to it

halkyon_meditate_server and its generated client, copied from Todo's
and stripped to the module, the register and the sync engine (ADR 0038,
D1, D7): content_key, meditate_settings and sitting, synced and sealed,
each indexing spaceId and deleted with the person's space; two
migrations, the initial one and sittings (purely additive, the ADR
explains the SQL); ports 8280 to 8282 and PostgreSQL 8290 (D13).
Tests: the module's basics naming `meditate`, the sync engine refusing
calls without a session, the register's modes, and a person's deletion
taking their rows alone.

halkyon_base's forwarding page knows Meditate's ways back
(meditate-loopback on 43826, meditate-scheme app.halkyon.meditate),
which halkyon_app's repository names among the apps' ports.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

apps/meditate/halkyon_meditate_server/lib/server.dart

@@ -0,0 +1,33 @@
+import 'package:halkyon_base_server/base.dart';
+import 'package:halkyon_meditate_server/src/generated/serverpod.dart';
+import 'package:halkyon_meditate_server/src/meditate_base.dart';
+import 'package:halkyon_meditate_server/src/pruning.dart';
+import 'package:serverpod_auth_idp_server/core.dart';
+
+/// The starting point of Halkyon Meditate's server.
+Future<void> run(List<String> args) async {
+  // The generated Serverpod is already connected with the generated code.
+  final pod = Serverpod(args);
+  // What every Halkyon server has (ADR 0014): sign-in, the account and its
+  // deletion, the pruning, the instance's basics, set up for Meditate; a member
+  // of the instance's register where the operator names one (ADR 0016).
+  HalkyonBase.configure(
+    pod,
+    meditateBase(accounts: AccountsMode.fromEnvironment()),
+  );
+  // Token managers validate and issue authentication keys; identity
+  // providers are the ways people can sign in (halkyon_base's
+  // auth_config.dart).
+  pod.initializeAuthServices(
+    tokenManagerBuilders: tokenManagerBuilders,
+    identityProviderBuilders: identityProviderBuilders(pod),
+  );
+
+  // The calls between the instance's services, on the web server
+  // (ADR 0016); Caddy never forwards them.
+  addInstanceRoutes(pod);
+
+  await pod.start();
+
+  await schedulePruning(pod);
+}