feat(todo): the app on halkyon_app, with its own icon

Todo's app is halkyon_app's instance and session gates with Todo's
frame ("Todo" under "Halkyon", its icon, its own sentences) and an
instance check accepting only `todo`; TodoDependencies on an instance,
an empty TodoPerson per person, nothing kept or synced yet. A person
sees an empty home and their account: whose it is on which instance,
switching account, signing out and deleting it (each asking first where
it deletes), and About with the source of what the instance runs and
the licence list. Texts in British English and German. App ID
app.halkyon.todo on every platform, GitHub's callback scheme registered
on Android, no web build.

Its icon is Lucide's list-checks (lucide-static 1.50.0) in the brand's
blues on white: tool/app_icons.py draws its strokes with Pillow and
writes every platform's launcher icon; Lucide's ISC notice joins the
licence list.

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/todo/halkyon_todo_flutter/analysis_options.yaml

@@ -1,40 +1,17 @@
-# This file configures the analyzer, which statically analyzes Dart code to
-# check for errors, warnings, and lints.
-#
-# The issues identified by the analyzer are surfaced in the UI of Dart-enabled
-# IDEs (https://dart.dev/tools#ides-and-editors). The analyzer can also be
-# invoked from the command line by running `flutter analyze`.
+# The workspace's lint rules (see ../../../analysis_options.yaml), minus the platform
+# folders and generated code.
+include: ../../../analysis_options.yaml
 
-# The following line activates a set of recommended lints for Flutter apps,
-# packages, and plugins designed to encourage good coding practices.
-include: package:flutter_lints/flutter.yaml
-
-linter:
-  # The lint rules applied to this project can be customized in the
-  # section below to disable rules from the `package:flutter_lints/flutter.yaml`
-  # included above or to enable additional rules. A list of all available lints
-  # and their documentation is published at
-  # https://dart-lang.github.io/linter/lints/index.html.
-  #
-  # Instead of disabling a lint rule for the entire project in the
-  # section below, it can also be suppressed for a single line of code
-  # or a specific dart file by using the `// ignore: name_of_lint` and
-  # `// ignore_for_file: name_of_lint` syntax on the line or in the file
-  # producing the lint.
-  rules:
-    # avoid_print: false  # Uncomment to disable the `avoid_print` rule
-    # prefer_single_quotes: true  # Uncomment to enable the `prefer_single_quotes` rule
-# Additional information about this file can be found at
-# https://dart.dev/guides/language/analysis-options
-
-formatter:
-  trailing_commas: preserve
 analyzer:
   exclude:
     - build/**
     - android/**
     - ios/**
-    - web/**
     - windows/**
     - macos/**
     - linux/**
+    # Generated by gen-l10n (see l10n.yaml).
+    - lib/l10n/app_localizations*.dart
+
+formatter:
+  trailing_commas: preserve