feat: each app's own colour, errors a true red, part of Halkyon Days (ADR 0045, D18, D19)

halkyone_ui's theme takes the app's own colour as its primary
(AppPrimary, appTheme(primary:)): Halkyon, Train and Meditate cobalt as
before, Myrmex strawberry once it asks for it. Filled and floating
buttons fill with its deep shade in both modes, white on it, and the
first start and the operator's screen wash in it. Errors become a true
red in every app, #B3261E light and #FF6B5E dark, far in hue from
Myrmex's strawberry, which Material's crimson stood beside (D19).

An app with a name of its own shows it alone in its wordmark, in its
colour (BrandWordmark.alone, LaunchScreen.alone, AppFrame.productAlone).
About says the app is part of Halkyon Days, as does the foot of the
instance's pages: profiles, privacy, invitations (D1). A secret's file
keeps an instance's domain whole where the app is named as it
(halkyon.li, not li).

ADR 0045 records D18 and D19, the names step 4 keeps, and step 3 built.

Whats-New: Errors show in a clearer red, and About says the app is part of Halkyon Days.
Whats-New-De: Fehler erscheinen in einem klareren Rot, und „Über“ nennt Halkyon Days, zu dem die App gehört.
Signed-off-by: Tizian 「ティツィアーン」 <c.3a8bz@simplelogin.com>
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

packages/halkyone_app/lib/l10n/halkyone_app_en.arb

@@ -141,6 +141,10 @@
   "accountDeleteTitle": "Delete your account?",
   "accountSignOutFailed": "Couldn't sign out on this device. Try again.",
   "accountDeleteFailed": "Couldn't delete your account: the instance wasn't reached. Try again.",
+  "aboutPartOf": "Part of Halkyon Days",
+  "@aboutPartOf": {
+    "description": "About names the project every app is part of (Halkyon Days' ADR 0045, D1). Halkyon Days is a name: never translated."
+  },
   "aboutSourceCode": "The source of what this instance runs:",
   "aboutSourceUnreachable": "Couldn't reach this instance to ask where its source is.",
   "sessionUnreachable": "Couldn't reach the server.",