chore: Halkyon Learn moves into apps/learn

Its server, client, app and curator, and the tools that write its
assets (maps, Anki fixtures, icons), as they are; paths are fixed in
the commits that follow.

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

halkyon_learn_server/config/development.yaml

@@ -1,76 +0,0 @@
-# This is the configuration file for your local development environment. By
-# default, it runs a single server on port 8080. To set up your server, you will
-# need to add the name of the database you are connecting to and the user name.
-# The password for the database is stored in the config/passwords.yaml.
-#
-# When running your server locally, the server ports are the same as the public
-# facing ports.
-
-# Configuration for the main API server.
-apiServer:
-  port: 8080
-  publicHost: localhost
-  publicPort: 8080
-  publicScheme: http
-
-# Configuration for the Insights server.
-insightsServer:
-  port: 8081
-  publicHost: localhost
-  publicPort: 8081
-  publicScheme: http
-
-# Configuration for the web server.
-webServer:
-  port: 8082
-  publicHost: localhost
-  publicPort: 8082
-  publicScheme: http
-
-# This is the database setup for your server.
-database:
-  host: localhost
-  port: 8090
-  name: halkyon_learn
-  user: postgres
-  #requireSsl: true # defaults to false
-  #isUnixSocket: true # defaults to false
-  dataPath: .serverpod/development/pgdata
-  #maxConnectionCount: 10 # Defaults to 10, a negative or null value removes the limit
-
-# This is the setup for Redis.
-redis:
-  enabled: false
-  host: localhost
-  port: 8091
-  #user: # defaults to empty
-  #requireSsl: true # defaults to false
-
-maxRequestSize: 524288 # The maximum size of requests allowed in bytes
-
-sessionLogs:
-  persistentEnabled: false
-  consoleEnabled: true
-  consoleLogFormat: text # Defaults to "json", options are "text" or "json"
-
-# futureCallExecutionEnabled: true # Defaults to true
-
-#futureCall:
-#  concurrencyLimit: 1 # Defaults to 1, a negative or null value removes the limit
-#  scanInterval: 5000 # Unit in milliseconds, defaults to 5000
-
-# Recommended when serving web clients: keeps auth tokens in httpOnly
-# cookies. Without this, web tokens live in JavaScript-readable storage,
-# where any XSS can steal them. Web clients opt in with
-# `client.cookieAuth = true`. Requires `allowedOrigins`; browsers from
-# origins not in the list lose cross-origin access, including to public
-# endpoints.
-#authCookie:
-#  secure: false # Cookies require https; relax only for http://localhost
-#  #name: serverpod_auth # Defaults to "serverpod_auth"
-#  #refreshName: serverpod_auth_refresh # Defaults to "<name>_refresh"
-#  #domain: example.com # Defaults to host-only; set to share across subdomains
-#  #path: / # Defaults to "/"
-#  #sameSite: lax # Defaults to "lax", options are "strict" or "none"
-#allowedOrigins:
-#  - http://localhost:8082 # The origin serving your Flutter web app