feat: Introduce dynamic tab management, sidebar, and search bar components, update backend database schema, and remove old SQL schema.

docs/development/ZENTRAL.md

@@ -6,3 +6,7 @@ File riassuntivo dello stato di sviluppo di Zentral.
 
 - [2025-12-02 Rebranding Apollinare to Zentral](./log/2025-12-02_rebranding.md) - **Completato**
   - Rinomina completa del progetto (Backend & Frontend).
+- [2025-12-03 UI Restructuring](./devlog/2025-12-03_ui_restructuring.md) - **Completato**
+  - Ristrutturazione interfaccia: Sidebar a 2 livelli, Tabs, SearchBar.
+- [2025-12-03 Backend Fix](./devlog/2025-12-03_backend_fix.md) - **Completato**
+  - Fix mancata migrazione database e avvio backend.

docs/development/devlog/2025-12-03_backend_fix.md

@@ -0,0 +1,17 @@
+# Backend Fix - Sync Model Changes
+
+## Problem
+The backend was failing to start with a `System.InvalidOperationException` because the `ZentralDbContext` model had pending changes that were not captured in a migration.
+
+## Solution
+1.  Created a new migration `SyncModelChanges` to synchronize the database schema with the code.
+    - Command: `dotnet ef migrations add SyncModelChanges --project Zentral.Infrastructure --startup-project Zentral.API`
+2.  Updated the database.
+    - Command: `dotnet ef database update --project Zentral.Infrastructure --startup-project Zentral.API`
+
+## Status
+- [x] Create Migration
+- [x] Update Database
+- [x] Verify Backend Startup
+
+The backend now starts correctly and listens on the configured port.

docs/development/devlog/2025-12-03_ui_restructuring.md

@@ -0,0 +1,53 @@
+# UI Restructuring Plan
+
+## Objective
+Restructure the graphical interface according to the guidelines:
+- 2-level sidebar (Apps -> Functions).
+- Top search bar.
+- Tabbed interface for the main viewport.
+- Responsive design.
+
+## Components to Create/Update
+
+### 1. TabContext (`src/frontend/src/contexts/TabContext.tsx`)
+- **State**:
+  - `tabs`: Array of `{ id: string, path: string, label: string, icon?: ReactNode }`.
+  - `activeTabPath`: string.
+- **Actions**:
+  - `openTab(tab)`: Adds tab if not exists, sets as active.
+  - `closeTab(path)`: Removes tab. If active, switches to neighbor.
+  - `setActiveTab(path)`: Updates active tab.
+- **Persistence**: Save `tabs` and `activeTabPath` to `localStorage`.
+
+### 2. TabsBar (`src/frontend/src/components/TabsBar.tsx`)
+- Renders the list of open tabs using MUI `Tabs` or a custom horizontal list.
+- Handles click (navigate) and close actions.
+- Mobile: Show as a popup or scrollable bar.
+
+### 3. Sidebar (`src/frontend/src/components/Sidebar.tsx`)
+- Refactor existing Drawer content.
+- Implement nested lists (Accordion style) for Modules.
+- Structure:
+  - **Core**: Dashboard, Calendar, Events, Clients, Location, Articles, Resources.
+  - **Warehouse**: Dashboard, Articles, Locations, Movements, Stock, Inventory.
+  - **Purchases**: Suppliers, Orders.
+  - **Sales**: Orders.
+  - **Production**: Dashboard, Orders, BOM, Work Centers, Cycles, MRP.
+  - **Admin**: Modules, Auto Codes, Custom Fields.
+
+### 4. SearchBar (`src/frontend/src/components/SearchBar.tsx`)
+- Input field in AppBar.
+- Filters available menu items.
+- On selection, opens the corresponding tab.
+
+### 5. Layout (`src/frontend/src/components/Layout.tsx`)
+- Integrate `Sidebar`, `SearchBar`, and `TabsBar`.
+- Ensure responsive behavior.
+
+## Execution Steps
+1. Create `TabContext`.
+2. Create `TabsBar`.
+3. Refactor `Layout` to include `TabsBar` and use `TabContext`.
+4. Create `Sidebar` with nested structure.
+5. Create `SearchBar` and integrate into `Layout`.
+6. Verify functionality.