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/09-ourdigital-backoffice/README.md

@@ -0,0 +1,86 @@
+# OurDigital Backoffice
+
+Business document creation for OurDigital consulting services.
+
+## Purpose
+
+Generate professional business documents:
+- Quotes and estimates (견적서)
+- Service proposals (제안서)
+- Contract drafts (계약서 초안)
+- Cost-benefit analysis (비용 분석)
+
+## Activation
+
+Only activates with "ourdigital" keyword:
+- "ourdigital 견적서 작성해줘"
+- "ourdigital proposal for [client]"
+- "ourdigital cost analysis"
+
+## Important Notice
+
+⚠️ **Legal Disclaimer**: Contract drafts require professional legal review before use.
+
+## Structure
+
+```
+09-ourdigital-backoffice/
+├── code/
+│   ├── SKILL.md
+│   └── scripts/
+│       ├── generate_quote.py
+│       ├── create_proposal.py
+│       ├── cost_analysis.py
+│       └── export_document.py
+├── desktop/
+│   ├── SKILL.md
+│   └── skill.yaml
+├── shared/
+│   ├── references/
+│   │   └── pricing-guide.md
+│   └── templates/
+│       ├── quote-template.md
+│       ├── proposal-template.md
+│       └── contract-template.md
+├── docs/
+│   └── CHANGELOG.md
+└── README.md
+```
+
+## Document Types
+
+| Type | Purpose | Turnaround |
+|------|---------|------------|
+| Quote | Pricing summary | Immediate |
+| Proposal | Detailed offering | 1-2 days |
+| Contract | Legal agreement | Requires review |
+| Cost Analysis | ROI justification | 1 day |
+
+## Service Catalog
+
+### SEO Services
+- Technical Audit: 300-500만원
+- Monthly SEO: 150-300만원/월
+- Local SEO: 100-200만원/월
+
+### Data & Analytics
+- GTM Setup: 200-400만원
+- GA4 Implementation: 150-300만원
+- Dashboard Development: 300-600만원
+
+### Consulting & Training
+- Brand Consulting: 500-1000만원
+- Marketing Strategy: 300-700만원
+- Workshop: 100-200만원/회
+
+## Integration
+
+Works with:
+- `01-ourdigital-brand-guide` - Document styling
+- `05-ourdigital-document` - Presentation format
+- Google Docs, Word export
+
+## Version
+
+- Current: 1.0.0
+- Author: OurDigital