feat: add update instructions dialog, email notifications, and capture date sorting

- Add Update Instructions Dialog with environment-specific commands (Docker/Git/Standalone)
- Add email notification settings for new version alerts
- Add "Sort by Capture Date" option using EXIF metadata extraction
- Fix E2E tests by loading environment variables via dotenv
- Add test-images/ and backend/*.db to .gitignore

Closes #181

backend/src/services/environmentService.js

@@ -0,0 +1,195 @@
+/**
+ * Environment Detection Service
+ * Detects the deployment environment and generates update instructions accordingly.
+ */
+
+const fs = require('fs');
+const path = require('path');
+const logger = require('../utils/logger');
+
+/**
+ * Detect the current deployment environment
+ * @returns {Object} Environment information
+ */
+async function detectEnvironment() {
+  // Check for Docker environment
+  const isDocker = fs.existsSync('/.dockerenv') ||
+                   process.env.DOCKER_CONTAINER === 'true';
+
+  // Determine project root (services -> src -> backend)
+  const projectRoot = path.join(__dirname, '../../..');
+
+  // Check for git repository
+  const isGit = fs.existsSync(path.join(projectRoot, '.git'));
+
+  // Check for docker-compose files
+  const hasDockerCompose = fs.existsSync(path.join(projectRoot, 'docker-compose.yml')) ||
+                           fs.existsSync(path.join(projectRoot, 'docker-compose.yaml'));
+
+  // Get app version
+  let appVersion = '0.0.0';
+  try {
+    const packagePath = path.join(__dirname, '../../package.json');
+    const packageContent = fs.readFileSync(packagePath, 'utf8');
+    const packageJson = JSON.parse(packageContent);
+    appVersion = packageJson.version || '0.0.0';
+  } catch (err) {
+    logger.warn('Could not read package.json for version:', err.message);
+  }
+
+  // Determine environment type
+  let type;
+  if (isDocker) {
+    type = 'docker';
+  } else if (isGit) {
+    type = 'git';
+  } else {
+    type = 'standalone';
+  }
+
+  return {
+    type,
+    isDocker,
+    isGit,
+    hasDockerCompose,
+    platform: process.platform,
+    nodeVersion: process.version,
+    appVersion
+  };
+}
+
+/**
+ * Generate environment-specific update instructions
+ * @param {Object} env - Environment info from detectEnvironment()
+ * @param {string} targetVersion - Target version to update to
+ * @returns {Object} Update instructions with pre-checks, steps, and post-checks
+ */
+function generateUpdateInstructions(env, targetVersion) {
+  const instructions = {
+    preChecks: [
+      {
+        id: 'backup',
+        text: 'I have backed up my database',
+        required: true
+      },
+      {
+        id: 'no-uploads',
+        text: 'No uploads are currently in progress',
+        required: true
+      },
+      {
+        id: 'downtime-aware',
+        text: 'I understand the application will restart during update',
+        required: false
+      }
+    ],
+    steps: [],
+    postChecks: [
+      'Verify the application starts correctly',
+      'Check the version in Admin -> System',
+      'Review release notes for any breaking changes or required actions'
+    ],
+    warnings: []
+  };
+
+  if (env.isDocker) {
+    instructions.environmentName = 'Docker';
+    instructions.steps = [
+      {
+        description: 'Pull latest images',
+        command: 'docker compose pull',
+        note: 'Downloads the new version images'
+      },
+      {
+        description: 'Recreate containers with new images',
+        command: 'docker compose up -d',
+        note: 'Restarts containers with new version'
+      },
+      {
+        description: 'Watch logs for startup (optional)',
+        command: 'docker compose logs -f backend',
+        note: 'Press Ctrl+C to exit logs',
+        optional: true
+      }
+    ];
+    instructions.warnings.push('Make sure you are in the directory containing your docker-compose.yml file');
+  } else if (env.isGit) {
+    instructions.environmentName = 'Git (Development)';
+    instructions.steps = [
+      {
+        description: 'Fetch latest changes',
+        command: 'git fetch origin',
+        note: 'Downloads references from remote'
+      },
+      {
+        description: 'Switch to new version tag',
+        command: `git checkout v${targetVersion}`,
+        note: 'Switches to the release version'
+      },
+      {
+        description: 'Install backend dependencies',
+        command: 'cd backend && npm install',
+        note: 'Updates npm packages'
+      },
+      {
+        description: 'Build frontend',
+        command: 'cd frontend && npm install && npm run build',
+        note: 'Compiles the frontend application'
+      },
+      {
+        description: 'Run database migrations',
+        command: 'cd backend && npm run migrate',
+        note: 'Updates database schema'
+      },
+      {
+        description: 'Restart application',
+        command: '# Restart your application (pm2, systemd, etc.)',
+        note: 'Method depends on your setup - e.g., pm2 restart picpeak'
+      }
+    ];
+    instructions.warnings.push('Adjust the restart command based on your process manager (pm2, systemd, etc.)');
+  } else {
+    instructions.environmentName = 'Standalone';
+    instructions.steps = [
+      {
+        description: 'Download release archive',
+        command: `# Download v${targetVersion} from GitHub Releases`,
+        note: `https://github.com/the-luap/picpeak/releases/tag/v${targetVersion}`
+      },
+      {
+        description: 'Backup current installation',
+        command: '# Create backup of current files',
+        note: 'Keep a copy of your current installation'
+      },
+      {
+        description: 'Extract and replace application files',
+        command: '# Extract release archive to installation directory',
+        note: 'Preserve your .env file and storage directory'
+      },
+      {
+        description: 'Install dependencies',
+        command: 'cd backend && npm install --production',
+        note: 'Updates npm packages'
+      },
+      {
+        description: 'Run database migrations',
+        command: 'cd backend && npm run migrate',
+        note: 'Updates database schema'
+      },
+      {
+        description: 'Restart application',
+        command: '# Restart your application service',
+        note: 'Method depends on your setup'
+      }
+    ];
+    instructions.warnings.push('Make sure to preserve your .env file and storage directory when updating');
+    instructions.warnings.push('Consider creating a full backup before updating');
+  }
+
+  return instructions;
+}
+
+module.exports = {
+  detectEnvironment,
+  generateUpdateInstructions
+};