feat(04-04): slug resolution + multi-project client dashboard + slug edit

- validate-slug API route: resolves clients.slug for Edge middleware
- proxy.ts: slug-first resolution (D-06) — tries slug then falls back to token
- client-view.ts: complete rewrite — getClientWithProjectsByToken + getProjectView
  - No quote_items, no payment amounts in client API (CLAUDE.md security invariants)
- client/[token]/page.tsx: multi-project dashboard — 1 project = direct view,
  2+ projects = shadcn Tabs with project names (D-09/D-10)
- edit/page.tsx: slug field with link preview + unique constraint error handling
- actions.ts: updateClient now persists slug, redirects on success/slug_taken

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.planning/phases/04-progetti-multi-project/04-03-SUMMARY.md

@@ -0,0 +1,52 @@
+---
+plan: "04-03"
+phase: "04-progetti-multi-project"
+status: complete
+completed_at: "2026-05-22"
+---
+
+# Summary: 04-03 — Project Workspace + Timer Analytics + Settings
+
+## What Was Built
+
+**`/admin/projects/[id]`** — full project workspace with 7 tabs: Fasi & Task, Pagamenti, Documenti, Note, Commenti, Preventivo, Timer. Reuses all existing tab components (PhasesTab, PaymentsTab, DocumentsTab, CommentsTab, QuoteTab) unchanged by passing `projectId` as `clientId`.
+
+**`ProfitabilityCard`** (`src/components/admin/ProfitabilityCard.tsx`) — pure display component (no `"use client"`). Shows: ore lavorate, importo accettato, €/h reale, €/h target, costo ideale, delta (verde = guadagno, rosso = perdita). Delta shown only when both hours > 0 and accepted > 0.
+
+**`TimerTab`** (`src/components/admin/tabs/TimerTab.tsx`) — client component wrapping TimerCell + ProfitabilityCard. Passes `projectId` as `clientId` to TimerCell (prop name is legacy; the underlying startTimer already uses project_id).
+
+**`/admin/impostazioni`** — settings page with target_hourly_rate form. Inline server action calls `updateSetting(SETTINGS_KEYS.TARGET_HOURLY_RATE, ...)`. Default value 50€/h from `getTargetHourlyRate()`.
+
+## Key Architectural Decision: resolveEntity()
+
+The tab components (PhasesTab, PaymentsTab, etc.) hardcode imports from `@/app/admin/clients/[id]/actions`. Rather than duplicating tab components or injecting actions as props, added `resolveEntity(id)` helper to both `actions.ts` and `quote-actions.ts`:
+
+```typescript
+async function resolveEntity(id: string): Promise<{ projectId: string | null; path: string }> {
+  // Checks if id is a projects.id directly (one PK lookup)
+  // Falls back to client_id lookup if not found
+  // Returns correct revalidatePath for either context
+}
+```
+
+This makes all existing tab actions work transparently with both clientId and projectId. Zero changes to tab components.
+
+**`updateAcceptedTotal` in `actions.ts`** — special case: detects project vs client context and updates the correct table (`projects.accepted_total` vs `clients.accepted_total`), with per-project payment stub splitting.
+
+**`timer-actions.ts`** — added `revalidatePath("/admin/projects")` and `revalidatePath(\`/admin/projects/${projectId}\`)` so the project list and workspace refresh after timer start/stop.
+
+## Files Changed
+
+| File | Action |
+|------|--------|
+| `src/app/admin/clients/[id]/actions.ts` | Updated — added resolveEntity(), all functions now work with projectId |
+| `src/app/admin/clients/[id]/quote-actions.ts` | Updated — same resolveEntity pattern |
+| `src/app/admin/timer-actions.ts` | Updated — added /admin/projects revalidation |
+| `src/components/admin/ProfitabilityCard.tsx` | Created |
+| `src/components/admin/tabs/TimerTab.tsx` | Created |
+| `src/app/admin/projects/[id]/page.tsx` | Created |
+| `src/app/admin/impostazioni/page.tsx` | Created |
+
+## Notes Tab
+
+No `NotesTab` component exists — notes rendered inline in the project workspace page. Simple read-only display (no add/edit/delete — consistent with how notes appear in the client dashboard).