feat(desktop): signature updater Tauri + wizard persistant + protocole E2E (#77)

- Signature des mises a jour Tauri : paire de cles minisign generee, cle publique dans tauri.conf.json, createUpdaterArtifacts actif, secrets CI exposes (repli build non signe si secret absent).

- Wizard 1er lancement : etat persistant wizard_done cote Rust (get_wizard_state/complete_wizard) pour ne plus reafficher la banniere, retro-compatible.

- Protocole des 6 tests E2E manuels : docs/DESKTOP_E2E_CHECKLIST.md.

- CI : desktop.test.mjs ajoute au job lint.

- Docs : ROADMAP, fiche desktop-tauri, CHANGELOG, README desktop, guide releases.

- fix(build): retirer les libs WeasyPrint inutiles du stage builder Docker.

Dockerfile

@@ -3,7 +3,8 @@
 FROM python:3.11-slim AS builder
 
 RUN apt-get update \
-    && apt-get install -y --no-install-recommends gcc libffi-dev libc6-dev libpango-1.0-0 libpangocairo-1.0-0 shared-mime-info \
+    && apt-get install -y --no-install-recommends gcc libffi-dev libc6-dev \
+    && apt-get clean \
     && rm -rf /var/lib/apt/lists/*
 
 WORKDIR /build
@@ -25,6 +26,7 @@ COPY --from=builder /install /usr/local
 # WeasyPrint runtime dependencies
 RUN apt-get update \
     && apt-get install -y --no-install-recommends libpango-1.0-0 libpangocairo-1.0-0 shared-mime-info \
+    && apt-get clean \
     && rm -rf /var/lib/apt/lists/*
 
 # Copy application code