feat: add Dashboard navigation as presentation configuration

Phase 6D pass 1. The shell's navigation was a flat list of module ids, which
is not a usable experience — and the obvious fix carries an obvious trap.
Letting a module declare its folder, or modelling "Media" as something
Livestream and Video belong to, turns a rendering preference into
architecture: a folder becomes an owner, membership starts to look like a
dependency, and the flat module graph acquires a hierarchy nobody decided on.

So the rule comes first: a Dashboard group is a label on a rendering bucket.
No manifest, no version, no artifact, no API, no lifecycle; nothing depends on
it. Livestream depends on Video because it calls Video's functionality, and
that orders startup. Livestream is shown under Media, and that orders nothing.
No parent module, child module, owning module, or group-derived dependency
appears anywhere in the contracts.

No manifest change and no version 5. `manifest.name` has been required since
version 1 and already is the module's product identity, so the shell renders
"Livestream" instead of `livestream` with nothing added. `suggestedGroup` is
deliberately deferred rather than shipped: it would force a hard
manifest-version cutover for a hint, and its only correct semantics needs
initialization logic that risks a suggestion overwriting an administrator's
decision. Defaulting and ownership are different things.

Two Core tables (migration 0003) hold groups and placements — server-side,
because a church configures its Dashboard rather than one browser;
platform-global, because no organization model exists to scope them to.
`group_id` is `on delete set null`, so deleting a group ungroups its modules
and a dangling reference is impossible. `module_id` carries no foreign key,
because modules are packages rather than rows, so a placement for an
uninstalled module is retained and restores its position on reinstall.

`resolveDashboardNavigation` is a pure function of configuration plus the
mountable set: an unplaced module is ungrouped and visible with no
initialization write, an absent module renders nothing, empty groups are kept,
and ordering is total with the module id as final tie-break.

`GET /api/v1/dashboard/navigation` returns the resolved view, layered on top of
the host-neutral module UI inventory rather than merged into it — each generic
descriptor is embedded untouched, so a standalone host never inherits Dashboard
semantics. Reading needs the permission the inventory already needs; organizing
needs the new platform permission `core.dashboard.navigation.manage` through a
narrow, idempotent, closed-validation mutation contract. No editor UI.

The flatness rule is executable: a test discovers real fixtures with a genuine
dependency, arranges them four ways including both in one folder and the
dependency inverted in presentation, and asserts discovery order, dependency
declarations, and the module set stay byte-identical. The end-to-end test
organizes a real installation through the real API, mounts a module from inside
a group, moves it, and asserts the navigation entry is byte-identical across the
move and still mounts the same artifact.

The shell's client for the generic inventory became dead code and was removed
rather than kept speculatively; the endpoint itself is unchanged.

Co-Authored-By: Claude Opus 5 <[email protected]>

docs/development/security.md

@@ -152,6 +152,22 @@ shell owns the container, the loading state, and every error, so a failing modul
 rather than the shell. None of that is containment: once imported, a module UI is ordinary same-realm
 JavaScript, exactly as described above.
 
+### Dashboard arrangement is not an access control
+
+Dashboard groups and placements are presentation configuration
+([ADR 0027](../architecture/decisions/0027-dashboard-navigation-and-flat-modules.md)). Organizing the
+Dashboard requires the platform permission `core.dashboard.navigation.manage` (baseline
+`restricted`), and holding it **grants no module authority whatsoever**: moving a module into a
+folder changes one presentation row, and every module route stays enforced against its own declared
+permission exactly as before. Nothing in the navigation configuration is read by discovery,
+dependency resolution, module startup, or the authorization evaluator.
+
+Navigation is also not a way to hide anything. A module absent from a viewer's navigation is a
+rendering decision, never a restriction — server authorization remains the only thing that decides
+what a request may do. Reading navigation requires the same `core.modules.ui.read` the module UI
+inventory requires, so it discloses the same installed-module enumeration and nothing more; it
+carries no filesystem path, package root, or manifest internal.
+
 ### Client-side permission checks are not a security boundary
 
 A host may tell a module UI what permissions it believes the viewer holds