Standardize toast notifications for blockchain transactions

Implemented standardized error and success handling for blockchain transactions using the error-handler.ts utilities. This provides consistent, user-friendly, bilingual (EN/KMR) messaging across the app.

Changes:
- web/src/components/staking/StakingDashboard.tsx:
  * Import handleBlockchainError and handleBlockchainSuccess
  * Replace manual dispatchError parsing in bond() transaction
  * Replace manual dispatchError parsing in nominate() transaction
  * Replace manual dispatchError parsing in unbond() transaction
  * All transactions now show context-aware error messages
  * Success messages use template interpolation (e.g., "{{amount}} HEZ")

Benefits:
- Consistent error messaging across all blockchain operations
- Automatic bilingual support (English + Kurmanji)
- Proper error categorization (Staking, Identity, Tiki, etc.)
- User-friendly error descriptions instead of raw pallet errors
- Reduced code duplication (removed ~40 lines of manual error parsing)

This is Phase 1 of toast standardization. Other components with blockchain transactions (DEX, Governance, Treasury) should follow this pattern in future updates.

Pattern to follow:
```typescript
if (dispatchError) {
  handleBlockchainError(dispatchError, api, toast);
} else {
  handleBlockchainSuccess('operation.key', toast, { param: value });
}
```

web/src/components/staking/StakingDashboard.tsx

@@ -22,6 +22,7 @@ import {
   type StakingInfo
 } from '@pezkuwi/lib/staking';
 import { LoadingState } from '@pezkuwi/components/AsyncComponent';
+import { handleBlockchainError, handleBlockchainSuccess } from '@pezkuwi/lib/error-handler';
 
 export const StakingDashboard: React.FC = () => {
   const { t } = useTranslation();
@@ -120,22 +121,10 @@ export const StakingDashboard: React.FC = () => {
             console.log('Transaction in block:', status.asInBlock.toHex());
 
             if (dispatchError) {
-              let errorMessage = 'Transaction failed';
+              handleBlockchainError(dispatchError, api, toast);
-              if (dispatchError.isModule) {
-                const decoded = api.registry.findMetaError(dispatchError.asModule);
-                errorMessage = `${decoded.section}.${decoded.name}: ${decoded.docs.join(' ')}`;
-              }
-              toast({
-                title: 'Error',
-                description: errorMessage,
-                variant: 'destructive',
-              });
               setIsLoading(false);
             } else {
-              toast({
+              handleBlockchainSuccess('staking.bonded', toast, { amount: bondAmount });
-                title: 'Success',
-                description: `Bonded ${bondAmount} HEZ successfully`,
-              });
               setBondAmount('');
               refreshBalances();
               // Refresh staking data after a delay
@@ -184,22 +173,10 @@ export const StakingDashboard: React.FC = () => {
         ({ status, dispatchError }) => {
           if (status.isInBlock) {
             if (dispatchError) {
-              let errorMessage = 'Nomination failed';
+              handleBlockchainError(dispatchError, api, toast);
-              if (dispatchError.isModule) {
-                const decoded = api.registry.findMetaError(dispatchError.asModule);
-                errorMessage = `${decoded.section}.${decoded.name}: ${decoded.docs.join(' ')}`;
-              }
-              toast({
-                title: 'Error',
-                description: errorMessage,
-                variant: 'destructive',
-              });
               setIsLoading(false);
             } else {
-              toast({
+              handleBlockchainSuccess('staking.nominated', toast, { count: selectedValidators.length.toString() });
-                title: 'Success',
-                description: `Nominated ${selectedValidators.length} validator(s)`,
-              });
               // Refresh staking data
               setTimeout(() => {
                 if (api && selectedAccount) {
@@ -242,21 +219,12 @@ export const StakingDashboard: React.FC = () => {
         ({ status, dispatchError }) => {
           if (status.isInBlock) {
             if (dispatchError) {
-              let errorMessage = 'Unbond failed';
+              handleBlockchainError(dispatchError, api, toast);
-              if (dispatchError.isModule) {
-                const decoded = api.registry.findMetaError(dispatchError.asModule);
-                errorMessage = `${decoded.section}.${decoded.name}: ${decoded.docs.join(' ')}`;
-              }
-              toast({
-                title: 'Error',
-                description: errorMessage,
-                variant: 'destructive',
-              });
               setIsLoading(false);
             } else {
-              toast({
+              handleBlockchainSuccess('staking.unbonded', toast, {
-                title: 'Success',
+                amount: unbondAmount,
-                description: `Unbonded ${unbondAmount} HEZ. Withdrawal available in ${bondingDuration} eras`,
+                duration: bondingDuration.toString()
               });
               setUnbondAmount('');
               setTimeout(() => {