feat(auth)+refactor(app): identifier at the access barrier; adopt the lib fidelity refactor

Consumer-side of the @ng-eventually/client fidelity pass, plus the identifier UX:

- Identity: the user types an IDENTIFIER at the access barrier (AccessGateScreen),
  in the same act that opens the shared wallet — the separate 'pick a username'
  screen (ConnexionScreen) is removed. The identifier is a technical id (a pseudo
  in practice, not a Festipod username), normalized (trim, @-stripped, lowercased)
  and persisted before the broker redirect, then handed to the SDK as the identity.
  AccountContext keeps its API but its stored value is now this normalized id.
- Relationship/connections are app-owned: new src/shared/utils/connections.ts holds
  the bilateral registry and maps each link to the SDK's directed grantRead(doc,
  grantee); the lib no longer carries a connection concept. Rewired FestipodData
  and the @data harness to it.
- Login removed: accounts use the SDK's IdentityStore (set/clear/get); no faux
  login/logout framing in the SDK boundary.

Doctrine reconciled: app-security (knowledge_authentication flow, knowledge_trust-model
directed grants, decision_2026-07-06_identifier-at-access-barrier), data-layer
(knowledge_context-internals: stable id principal + single-seed), app-architecture
(knowledge_screens auth inventory), bdd-testing (caveat_wallet-bloat-hang).

App gates: tsc no new errors, build OK. @data path unaffected (harness bypasses the
gate and sets identity directly; login() is not on that path).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

.project/concepts/app-architecture/_debt.md

@@ -1,7 +0,0 @@
-# Doc-debt — app-architecture
-
-> Presence of a block = doc to update. Processed → delete the block; no blocks left → delete this file.
-> One block = one "big change": `why` + `files` + `verify` (leaves to review).
-
-## Raw markers (consolidate into blocks, then delete)
-- TOUCHED src/shared/context/FestipodDataContext.tsx @2026-07-05 (session 0b064e8b-1717-421f-a20e-a4318ad217b1)

.project/concepts/app-architecture/knowledge_screens.md

@@ -30,9 +30,9 @@ Utilisé notamment par Storybook (voir concept `tech-stack`) pour parcourir les
 - **home/** : `welcome`, `home`, `settings`
 - **event/** : `events`, `event-detail`, `create-event`, `update-event`, `invite`, `participants-list`, `meeting-points`
 - **user/** : `profile`, `update-profile`, `user-profile`, `friends-list`, `share-profile`
-- **auth/** : `login`
+- **auth/** : `AccessGateScreen` — la **barrière d'accès** (login NextGraph + saisie de l'identifiant), rendue par `src/app/AuthGate.tsx`, **hors registre/routing** (ce n'est pas un écran routé). Les anciens `LoginScreen` puis `ConnexionScreen` ont été retirés (cf. concept `app-security`, [[knowledge_authentication]]).
 
-> Le mapping path → écran est dans [[knowledge_routing]]. La plupart des écrans consomment `useFestipodData()` (concept `data-layer`) ; exceptions : `LoginScreen`/`WelcomeScreen`.
+> Le mapping path → écran est dans [[knowledge_routing]]. La plupart des écrans consomment `useFestipodData()` (concept `data-layer`) ; exceptions : `WelcomeScreen` et la barrière `AccessGateScreen`.
 
 ## Piège : registre incomplet