feat(todo): the server on halkyon_base

Todo's server includes halkyon_base (ADR 0014), configured for Todo:
its basics say it serves `todo`, sign-in mails name Halkyon Todo, the
source is this repository, minimumAppBuild 1. Authentication through
the module (anonymous, GitHub, email codes, server-side sessions) in
place of the scaffold's email-and-password provider; the module's
pruning scheduled once however often the server starts. The scaffold's
greeting, its Flutter web hosting, cloud storage and Docker files go;
session logs are never persisted. Todo was never deployed, so its
migrations start again with one initial migration. The root's lints
apply, with the four constructor rules off as on Learn's server.

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

pubspec.lock

@@ -1,14 +1,6 @@
 # Generated by pub
 # See https://dart.dev/tools/pub/glossary#lockfile
 packages:
-  _discoveryapis_commons:
-    dependency: transitive
-    description:
-      name: _discoveryapis_commons
-      sha256: "55dd9e9cb83f8b62aa5dd8744d3bfedf79d33f9457c1684916c2b5c69c6e3a9b"
-      url: "https://pub.dev"
-    source: hosted
-    version: "1.0.8"
   _fe_analyzer_shared:
     dependency: transitive
     description:
@@ -17,14 +9,6 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "103.0.0"
-  amazon_cognito_identity_dart_2:
-    dependency: transitive
-    description:
-      name: amazon_cognito_identity_dart_2
-      sha256: ff3d493eb94d9dc624bd8f0a92bf49754e67d39717e6a52ff0c7dd14e5c0e20b
-      url: "https://pub.dev"
-    source: hosted
-    version: "3.8.2"
   analysis_server_plugin:
     dependency: transitive
     description:
@@ -800,14 +784,6 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "18.0.2"
-  google_cloud:
-    dependency: transitive
-    description:
-      name: google_cloud
-      sha256: b385e20726ef5315d302c5933bfb728103116c5be2d3d17094b01a82da538c1f
-      url: "https://pub.dev"
-    source: hosted
-    version: "0.5.0"
   google_fonts:
     dependency: transitive
     description:
@@ -864,22 +840,6 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "1.1.3"
-  googleapis:
-    dependency: transitive
-    description:
-      name: googleapis
-      sha256: d38bb64016ef27eca7fde992994b9d2999bcea307685807e15d6a08bff05dc61
-      url: "https://pub.dev"
-    source: hosted
-    version: "17.0.0"
-  googleapis_auth:
-    dependency: transitive
-    description:
-      name: googleapis_auth
-      sha256: d31822528becea550f7c7a9ab73a4518e31e48f201ab574be7e141f262923f27
-      url: "https://pub.dev"
-    source: hosted
-    version: "2.3.4"
   graphs:
     dependency: transitive
     description:
@@ -997,14 +957,6 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "1.0.0"
-  js:
-    dependency: transitive
-    description:
-      name: js
-      sha256: "53385261521cc4a0c4658fd0ad07a7d14591cf8fc33abbceae306ddb974888dc"
-      url: "https://pub.dev"
-    source: hosted
-    version: "0.7.2"
   json_annotation:
     dependency: transitive
     description:
@@ -1670,30 +1622,6 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "4.0.4"
-  serverpod_cloud_storage:
-    dependency: transitive
-    description:
-      name: serverpod_cloud_storage
-      sha256: "49d33119165b60020f900666eeae7751b695d200c86fd68a75c39410f6f61284"
-      url: "https://pub.dev"
-    source: hosted
-    version: "4.0.4"
-  serverpod_cloud_storage_gcp:
-    dependency: transitive
-    description:
-      name: serverpod_cloud_storage_gcp
-      sha256: "9861459d8707beb8d60ac174fc0ee8d7992fa4b966ccb1b9eeeb751ce3e3d46d"
-      url: "https://pub.dev"
-    source: hosted
-    version: "4.0.4"
-  serverpod_cloud_storage_s3_compat:
-    dependency: transitive
-    description:
-      name: serverpod_cloud_storage_s3_compat
-      sha256: e2639d1cf21c82a2b86876584480241da51cbde8fc59de12e7f6a7ae39b4fd70
-      url: "https://pub.dev"
-    source: hosted
-    version: "4.0.4"
   serverpod_database:
     dependency: transitive
     description: