fix: Add user-facing error notifications for failed operations

Add toast notifications using react-hot-toast across the application to
inform users when operations fail. This addresses issue #13 which
identified that multiple components catch errors without displaying
user-facing notifications.

Components updated:
- SettingsPanel: Shows toast on company info fetch failure
- TeamList: Shows toast on employee data retrieval failure
- TimeEntryModal: Shows toast on save/delete failures, success on completion
- AuthProvider: Shows toast on login/logout failures
- tokenService: Shows toast on session expiry and auth failures
- timeEntryService: Shows toast on sync success/failure with entry counts

Closes #13

Author: claude

src/components/settings/SettingsPanel.tsx

@@ -1,6 +1,7 @@
 'use client';
 
 import { useState, useEffect } from 'react';
+import toast from 'react-hot-toast';
 import { Card } from '@/components/ui';
 import { bcClient } from '@/services/bc/bcClient';
 import { useAuth } from '@/services/auth';
@@ -38,6 +39,7 @@ export function SettingsPanel() {
       } catch (err) {
         console.error('Failed to fetch company info:', err);
         setError('Failed to load company information');
+        toast.error('Failed to load company information. Please try again.');
       } finally {
         setIsLoading(false);
       }

src/components/team/TeamList.tsx

@@ -1,6 +1,7 @@
 'use client';
 
 import { useState, useEffect } from 'react';
+import toast from 'react-hot-toast';
 import { TeamMemberCard } from './TeamMemberCard';
 import { Card } from '@/components/ui';
 import { bcClient } from '@/services/bc/bcClient';
@@ -51,6 +52,7 @@ export function TeamList() {
       } catch (err) {
         console.error('Failed to fetch employees:', err);
         setError('Failed to load team members');
+        toast.error('Failed to load team members. Please try again.');
       } finally {
         setIsLoading(false);
       }

src/components/timesheet/TimeEntryModal.tsx

@@ -1,6 +1,7 @@
 'use client';
 
 import { useState, useEffect } from 'react';
+import toast from 'react-hot-toast';
 import { TrashIcon } from '@heroicons/react/24/outline';
 import { Modal, Button, Input, Select } from '@/components/ui';
 import { useTimeEntriesStore, useProjectsStore } from '@/hooks';
@@ -113,9 +114,11 @@ export function TimeEntryModal({ isOpen, onClose, date, entry }: TimeEntryModalP
           isRunning: false,
         });
       }
+      toast.success(entry ? 'Time entry updated' : 'Time entry saved');
       onClose();
     } catch (error) {
       console.error('Failed to save entry:', error);
+      toast.error('Failed to save time entry. Please try again.');
     } finally {
       setIsSubmitting(false);
     }
@@ -131,9 +134,11 @@ export function TimeEntryModal({ isOpen, onClose, date, entry }: TimeEntryModalP
     setIsSubmitting(true);
     try {
       await deleteEntry(entry.id);
+      toast.success('Time entry deleted');
       onClose();
     } catch (error) {
       console.error('Failed to delete entry:', error);
+      toast.error('Failed to delete time entry. Please try again.');
     } finally {
       setIsSubmitting(false);
     }

src/services/auth/AuthProvider.tsx

@@ -1,6 +1,7 @@
 'use client';
 
 import { ReactNode, useEffect, useState } from 'react';
+import toast from 'react-hot-toast';
 import {
   MsalProvider,
   AuthenticatedTemplate,
@@ -80,6 +81,7 @@ export function useAuth() {
       await instance.loginRedirect(loginRequest);
     } catch (error) {
       console.error('Login failed:', error);
+      toast.error('Login failed. Please try again.');
       throw error;
     }
   };
@@ -91,6 +93,7 @@ export function useAuth() {
       });
     } catch (error) {
       console.error('Logout failed:', error);
+      toast.error('Logout failed. Please try again.');
       throw error;
     }
   };

src/services/auth/tokenService.ts

@@ -1,4 +1,5 @@
 import { PublicClientApplication, SilentRequest } from '@azure/msal-browser';
+import toast from 'react-hot-toast';
 import { msalConfig, bcTokenRequest, graphTokenRequest } from './msalConfig';
 
 let msalInstance: PublicClientApplication | null = null;
@@ -20,6 +21,7 @@ export async function getAccessToken(
 
     if (!account) {
       console.error('No active account found');
+      toast.error('Session expired. Please sign in again.');
       return null;
     }
 
@@ -41,6 +43,7 @@ export async function getAccessToken(
       return null;
     } catch (redirectError) {
       console.error('Failed to acquire token via redirect:', redirectError);
+      toast.error('Authentication failed. Please try signing in again.');
       return null;
     }
   }

src/services/bc/timeEntryService.ts

@@ -1,5 +1,6 @@
+import toast from 'react-hot-toast';
 import { bcClient } from './bcClient';
-import type { TimeEntry, BCJobJournalLine, Project, Task } from '@/types';
+import type { TimeEntry, BCJobJournalLine, Project } from '@/types';
 import { format, parseISO } from 'date-fns';
 
 // Local storage key for time entries (cached/pending sync)
@@ -147,6 +148,22 @@ export const timeEntryService = {
     }
 
     saveLocalEntries(entries);
+
+    // Show user-friendly notifications for sync results
+    if (synced > 0 && failed === 0) {
+      toast.success(
+        `Successfully synced ${synced} time ${synced === 1 ? 'entry' : 'entries'} to Business Central`
+      );
+    } else if (synced > 0 && failed > 0) {
+      toast.error(
+        `Synced ${synced} ${synced === 1 ? 'entry' : 'entries'}, but ${failed} failed. Please try again.`
+      );
+    } else if (failed > 0) {
+      toast.error(
+        `Failed to sync ${failed} time ${failed === 1 ? 'entry' : 'entries'}. Please try again.`
+      );
+    }
+
     return { synced, failed };
   },