feat: Add OurDigital custom skills package (10 skills)

Complete implementation of OurDigital skills with dual-platform support
(Claude Desktop + Claude Code) following standardized structure.

Skills created:
- 01-ourdigital-brand-guide: Brand reference & style guidelines
- 02-ourdigital-blog: Korean blog drafts (blog.ourdigital.org)
- 03-ourdigital-journal: English essays (journal.ourdigital.org)
- 04-ourdigital-research: Research prompts & workflows
- 05-ourdigital-document: Notion-to-presentation pipeline
- 06-ourdigital-designer: Visual/image prompt generation
- 07-ourdigital-ad-manager: Ad copywriting & keyword research
- 08-ourdigital-trainer: Training materials & workshop planning
- 09-ourdigital-backoffice: Quotes, proposals, cost analysis
- 10-ourdigital-skill-creator: Meta skill for creating new skills

Features:
- YAML frontmatter with "ourdigital" or "our" prefix triggers
- Standardized directory structure (code/, desktop/, shared/, docs/)
- Shared environment setup (_ourdigital-shared/)
- Comprehensive reference documentation
- Cross-skill integration support

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

custom-skills/_ourdigital-shared/.env.ourdigital.template

@@ -0,0 +1,69 @@
+# OurDigital Skills Environment Variables Template
+# Copy this file to .env.ourdigital and fill in your values
+# IMPORTANT: Never commit the actual .env.ourdigital file to version control
+
+# =============================================================================
+# Environment Settings
+# =============================================================================
+OURDIGITAL_ENV=development  # development | production
+OURDIGITAL_CONFIG_PATH=~/.ourdigital/config.yaml
+OURDIGITAL_CREDENTIALS_PATH=~/.ourdigital/credentials/
+
+# =============================================================================
+# Notion API
+# =============================================================================
+NOTION_API_TOKEN=secret_xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
+
+# Working with AI Database (primary export destination)
+NOTION_WORKING_WITH_AI_DB=f8f19ede-32bd-43ac-9f60-0651f6f40afe
+
+# OurDigital Channels Database
+NOTION_OURDIGITAL_CHANNELS_DB=9e958359535b495e863aba20d6c0a59b
+
+# =============================================================================
+# Ghost CMS
+# =============================================================================
+# blog.ourdigital.org (Korean blog)
+GHOST_BLOG_URL=https://blog.ourdigital.org
+GHOST_BLOG_ADMIN_KEY=
+
+# journal.ourdigital.org (English journal)
+GHOST_JOURNAL_URL=https://journal.ourdigital.org
+GHOST_JOURNAL_ADMIN_KEY=
+
+# ourstory.day (Personal essays)
+GHOST_OURSTORY_URL=https://ourstory.day
+GHOST_OURSTORY_ADMIN_KEY=
+
+# =============================================================================
+# Google APIs
+# =============================================================================
+GOOGLE_APPLICATION_CREDENTIALS=~/.ourdigital/credentials/google.json
+
+# Google Search Console
+GSC_PROPERTY_URL=https://www.ourdigital.org
+
+# Google Analytics 4
+GA4_PROPERTY_ID=
+
+# =============================================================================
+# Figma
+# =============================================================================
+FIGMA_ACCESS_TOKEN=
+
+# =============================================================================
+# n8n Workflow Automation
+# =============================================================================
+N8N_HOST_URL=https://n8n.dintelligence.co.kr
+N8N_API_KEY=
+
+# =============================================================================
+# Optional: AI Services
+# =============================================================================
+# ANTHROPIC_API_KEY=  # Usually set globally
+# OPENAI_API_KEY=     # For DALL-E integration
+
+# =============================================================================
+# Ulysses Export (macOS)
+# =============================================================================
+ULYSSES_EXPORT_PATH=~/Library/Mobile Documents/com~apple~CloudDocs/Ulysses/Blog Drafts/