Major updates: LinkedIn auto-posting, timezone fixes, and Docker improvements

Features:
- Add LinkedIn OAuth integration and auto-posting functionality
- Add scheduler service for automated post publishing
- Add metadata field to generated_posts for LinkedIn URLs
- Add privacy policy page for LinkedIn API compliance
- Add company management features and employee accounts
- Add license key system for company registrations

Fixes:
- Fix timezone issues (use UTC consistently across app)
- Fix datetime serialization errors in database operations
- Fix scheduling timezone conversion (local time to UTC)
- Fix import errors (get_database -> db)

Infrastructure:
- Update Docker setup to use port 8001 (avoid conflicts)
- Add SSL support with nginx-proxy and Let's Encrypt
- Add LinkedIn setup documentation
- Add migration scripts for schema updates

Services:
- Add linkedin_service.py for LinkedIn API integration
- Add scheduler_service.py for background job processing
- Add storage_service.py for Supabase Storage
- Add email_service.py improvements
- Add encryption utilities for token storage

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

.env.linkedin.example

@@ -0,0 +1,23 @@
+# LinkedIn Auto-Posting Configuration
+# Copy these lines to your .env file and fill in the values
+
+# ==================== LinkedIn API ====================
+# Create a LinkedIn app at: https://www.linkedin.com/developers/apps
+# Required OAuth scopes: openid, profile, email, w_member_social
+
+LINKEDIN_CLIENT_ID=your_linkedin_app_client_id
+LINKEDIN_CLIENT_SECRET=your_linkedin_app_client_secret
+LINKEDIN_REDIRECT_URI=https://yourdomain.com/settings/linkedin/callback
+
+# ==================== Token Encryption ====================
+# Generate with: python scripts/generate_encryption_key.py
+# ⚠️  IMPORTANT: Never change this key after storing tokens!
+
+ENCRYPTION_KEY=your_generated_fernet_key_here
+
+# ==================== Notes ====================
+# 1. Replace "yourdomain.com" with your actual domain
+# 2. Ensure HTTPS is enabled (required for OAuth)
+# 3. The redirect URI must match exactly in LinkedIn app settings
+# 4. Keep these values secure and never commit to git
+# 5. After setup, restart your application to load new variables