feat: SIWE auth, auto-pin, pin search/share, explorer improvements

- SIWE server-side auth (siwe + jose JWT)
- Wallet provider fallback (MAOS -> MetaMask)
- Auto-pin after upload (quick + crypto)
- Pin search/filter in explorer
- Share button (gateway link) per pin
- Copy CID button per pin
- Breadcrumb root navigation fix
- Hydration mismatch fix (mounted state)
- Defensive truncateCid for empty values
- CSP fix (template literal)
- Error boundaries (upload, profile, usage)
- 191 tests passing

src/components/payment/PaymentPanel.tsx

@@ -104,7 +104,11 @@ export default function PaymentPanel({
 
       await refreshPricing(result.address, fileSize);
     } catch (e: unknown) {
-      setError(e instanceof Error ? e.message : 'Failed to connect wallet');
+      const message = e instanceof Error ? e.message : 'Failed to connect wallet';
+      const isVaultLocked = message.toLowerCase().includes('vault locked') || 
+                           message.toLowerCase().includes('user rejected') ||
+                           message.toLowerCase().includes('user denied');
+      setError(isVaultLocked ? 'Ontgrendel je wallet eerst met je wachtwoord.' : message);
     } finally {
       setConnecting(false);
     }