refactor: convert repository to monorepo with npm workspaces

Restructured the repository into a monorepo to better organize application code
and maintenance scripts.

## Workspace Structure
- web-app: Next.js application (all app code moved from root)
- housekeeping: Database backup and maintenance scripts

## Key Changes
- Moved all application code to web-app/ using git mv
- Moved database scripts to housekeeping/ workspace
- Updated Dockerfile for monorepo build process
- Updated docker-compose files (volume paths: ./web-app/etc/hosts/)
- Updated .gitignore for workspace-level node_modules
- Updated documentation (README.md, CLAUDE.md, CHANGELOG.md)

## Migration Impact
- Root package.json now manages workspaces
- Build commands delegate to web-app workspace
- All file history preserved via git mv
- Docker build process updated for workspace structure

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

web-app/app/[locale]/share/bill/[id]/page.tsx

@@ -0,0 +1,41 @@
+import { fetchBillById } from '@/app/lib/actions/billActions';
+import { ViewBillCard } from '@/app/ui/ViewBillCard';
+import { Main } from '@/app/ui/Main';
+import { notFound } from 'next/navigation';
+import { validateShareAccess } from '@/app/lib/actions/locationActions';
+
+export default async function Page({ params: { id } }: { params: { id: string } }) {
+
+    // Split combined ID: shareId (40 chars) + '-' + billID (24 chars)
+    // ShareId = locationId (24) + checksum (16) = 40 chars
+    const shareId = id.substring(0, 40);
+    const billID = id.substring(41); // Skip the '-' separator
+
+    // Validate share access (checks checksum + TTL, extracts locationId)
+    const accessValidation = await validateShareAccess(shareId);
+
+    if (!accessValidation.valid || !accessValidation.locationId) {
+        return (
+            <Main>
+                <div className="alert alert-error">
+                    <p>{accessValidation.error || 'This content is no longer shared'}</p>
+                </div>
+            </Main>
+        );
+    }
+
+    const locationID = accessValidation.locationId;
+
+    // Fetch bill data
+    const [location, bill] = await fetchBillById(locationID, billID) ?? [];
+
+    if (!bill || !location) {
+        return notFound();
+    }
+
+    return (
+        <Main>
+            <ViewBillCard location={location} bill={bill} shareId={shareId} />
+        </Main>
+    );
+}