feat(journal): add JournalView UI with /journal route + nav link

Restores a working browser surface for the journal feature, which was
left UI-less when Stage F of the original plan was deferred. JournalView
is a fresh write (not a rename of BriefingView) — drops the briefing-
specific weather panel, news cards, RSS reactions, article-discuss
button, and setup wizard, since none of those have journal-backend
equivalents.

What it does:
- Fetches /api/journal/today on mount; shows today's daily-prep card
  (rendered from msg_metadata.kind === 'daily_prep' sections)
- Day picker via /api/journal/days lets you switch to past days
- Refresh-prep button hits /api/journal/trigger-prep
- Center is the existing ChatPanel pinned to today's journal conversation
  (so the chat input + SSE + tool-call cards inherit unchanged)
- Right sidebar keeps the upcoming-events list (uses the generic
  /api/events endpoint, not a briefing-specific one)

Also:
- Replace the dead Briefing API client functions with Journal equivalents
  (getJournalConfig, saveJournalConfig, getJournalToday, getJournalDay,
  getJournalDays, triggerJournalPrep, list/update/deleteJournalMoment).
- Remove NewsView.vue — it was orphaned (no route, no nav) and depended
  on the deleted /api/briefing/* endpoints. If a standalone news surface
  is wanted later it'll need to be rebuilt against new endpoints.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

frontend/src/router/index.ts

@@ -116,6 +116,11 @@ const router = createRouter({
       name: "calendar",
       component: () => import("@/views/CalendarView.vue"),
     },
+    {
+      path: "/journal",
+      name: "journal",
+      component: () => import("@/views/JournalView.vue"),
+    },
     {
       path: "/settings",
       name: "settings",