feat(learn,todo,train,meditate,ui): the navigation bar flush with the foot, a fade above it

Below medium windows the frame's bar is Material 3 Expressive's again,
flush with the window's foot (decided 7 Nov 2026 by the developer): the
theme's NavigationBar across the whole width, 64 dp in its own colour,
running on beneath the system's bar as Material's does. Right above it a
fade 32 dp high, from the background of the screen in view (the
ScreenTint's, the theme's surface before a screen claims one) made
see-through to that background, so what scrolls on beneath the bar fades
out rather than being cut off; taps pass through it. The rail of wider
windows stays as it was.

halkyon_ui's FloatingNavigationBar becomes FlushNavigationBar, its side
margin, lift and rounded card gone. Its coverOf is now the whole room
content leaves at its end, the system's bar included (the body's bottom
padding: bar, fade and system's bar inside the frame, the system's bar
alone outside it), and floating buttons rise by buttonLiftOf, the same
without the system's bar, which a Scaffold keeps them clear of itself.
Lists, Todo's hour grid and the Plan's sheet keep using coverOf; the
Profile's list no longer adds the system's bar a second time.

Whats-New: The navigation bar sits at the bottom edge again, with a soft fade above it.
Whats-New-De: Die Navigationsleiste sitzt wieder am unteren Rand, mit einem sanften Übergang darüber.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

AGENTS.md

@@ -8,7 +8,7 @@ Halkyon's apps and the packages they share, in one repository and one pub worksp
 
 - **`apps/<app>/`**: each app's packages, as `serverpod create` lays them out (`halkyon_<app>_server`, `_client`, `_flutter`), plus what is the app's alone (Learn's curator, the scripts writing Learn's assets in `apps/learn/tool/`, run from `apps/learn`; the apps' icons are the root's `tool/app_icons.py`, ADR 0031). Learn is the app that runs; Train, Todo and Meditate run too (ADR 0030, ADR 0033, ADR 0038), Todo and Meditate not released yet.
 - **`packages/`**: what the apps share, each with its README and licence, which the apps take by path (`path: ../../../packages/<package>`), so a change to a shared package and to the apps using it is one commit:
-  - `halkyon_ui`: Halkyon's look, the theme around cobalt and copper, Noto Sans bundled, the window-size classes and the widgets every screen is built of (the floating bar and rail, `FoldingTabs`' tab row folding into the title), with texts of its own (English, German).
+  - `halkyon_ui`: Halkyon's look, the theme around cobalt and copper, Noto Sans bundled, the window-size classes and the widgets every screen is built of (the navigation bar flush with the foot with its fade, and the rail, `FoldingTabs`' tab row folding into the title), with texts of its own (English, German).
   - `halkyon_base_server`, `halkyon_base_client`: the Serverpod module every Halkyon server includes (ADR 0014): signing in (a password with TOTP and the resets of ADR 0017, SimpleLogin on `halkyon_oidc`, email codes proving an address; no anonymous accounts since ADR 0020, D25, nor GitHub since D36), an account's ways in and its deletion with a hook for each app's own data, the pruning, the instance's basics, people's handles and public profiles, who may sign up (`SIGN_UP`: open, approval, closed) with the accounts waiting for approval and the instance's operators who approve them (Halkyon Learn's ADR 0021, step 1), the operator's assistants forwarded on halkyon_llm with their grants, each person's budget, the efforts they allow and counted figures, and the instance's privacy page made from its settings (step 2), and the instance's register (ADR 0016): one account per person across an operator's services, held by one service (Learn's server on learn.halkyon.eu) and asked by the others, its members (`ACCOUNT_REGISTER_URL`), all sharing a secret (`INSTANCE_SECRET`); its README says how.
   - `halkyon_app`: every app's shell on the module's client (ADR 0014): the instances a device keeps accounts on and the first start, signing in and switching person, the gates building an app's dependencies per instance and per person, the sync service and where it stands, the account section of an app's settings (`AccountTiles`), every app's Profile (`HalkyonProfile`, decided 2026-11-02: the person's own tab, the same in every app, with their account, the ways they sign in and their public profile, one for all apps, then the app's own tabs) and people's public profiles (`PublicProfileRepository`, `PublicProfileSection`, `showProfileOf`), the wait screen of an account waiting for approval and the operator's card, badge and screen (ADR 0021), the assistants of an app's settings (`AssistantsCard`: granted, by provider, agreed to, what is left of the person's budget, used, and the person's own keys) and the operator's grants from that screen (`AssistantGrantsScreen`: several assistants to several people at once, each with one budget, D57 to D63), with the repositories asking them through the module, at an effort the operator allows, or a person's own key directly (step 2) and what an app's warning before a private studyset goes names (`providerTermsOf`, `OwnAssistant.onThisMachine`, step 3), About with the instance's source link (`showAppAbout`), the device's own speech recognition (`SpeechInput`, `DeviceSpeechInput` on `speech_to_text`, `FakeSpeechInput` in `testing.dart`; none on Linux) and dictation into a text at its cursor, listening again after each pause (`Dictation`, Meditate's ADR 0038, D15; an app that listens declares the microphone and its usage texts itself), what's new after an update (`WhatsNew`, `WhatsNewOnUpdate`, `WhatsNewTile`, from the app's `assets/whats_new/`, Train's ADR 0030, D61), the device's appearance and language, chosen in Settings and applied before anyone signs in (`Look`, `FileLookStore`, `LookCubit`, `DeviceLookCard`; Learn keeps them among its own device settings and shows `LookSettingsCard`; ADR 0014's amendment of 4 Nov 2026), the language every app picks (`resolveAppLocale`) and countries' and subdivisions' names (Unicode CLDR's, bundled), with texts that name the app.
   - `halkyon_editor` (ADR 0033, D37, 6 Nov 2026): rich text, the general parts of Learn's editor on our fork of `appflowy_editor`: `RichContent` (the editor's document JSON, which Learn and Todo store), `RichContentEditor`, `RichContentView`, the format bar, links, the clipboard keeping formats, superscript and subscript, and `EditorBlocks`, through which an app adds blocks, marks within lines and their buttons (`basicBlocks` without any), with texts of its own (English, German). What is Learn's alone stays in Learn on top of it.