docs: add design plan for TFC to MC currency rebranding task

docs/dev/design/next-task-tfc-to-mc-currency-rebranding.md

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+**TASK: Complete Currency Rebranding - ThreeFold Credit (TFC) → Mycelium Credit (MC)**
+
+**Objective:** Systematically replace all instances of "ThreeFold Credit", "TFC", and related currency terminology with "Mycelium Credit" and "MC" throughout the Project Mycelium marketplace repository, implementing the new currency system with 1 MC = 1 USD base rate.
+
+**Requirements:**
+1. **Analyze Current Usage:** Use grep to find ALL instances of "TFC", "ThreeFold Credit", "TF Credit", "tfp", "TFP", "credits_usd", currency symbols, and wallet references across the entire codebase.
+
+2. **Categorize by File Type:** Backend (controllers, services, models), Frontend (views, JS), Tests, Docs/Specs, Configuration
+
+3. **Develop Replacement Strategy:** 
+   - **Backend (Code & Logic):**
+     - "TFC" → "MC"
+     - "ThreeFold Credit" → "Mycelium Credit" 
+     - "TF Credit" → "Mycelium Credit"
+     - "tfp" → "mc" (variable names)
+     - "TFP" → "MC" (constants/enums)
+     - `credits_usd` → `credits_mc` (if needed)
+     - Currency calculation logic (maintain 1:1 USD rate)
+   - **Frontend (Display text):**
+     - "ThreeFold Credit" → "Mycelium Credit"
+     - "TFC" → "MC" 
+     - Currency symbols and wallet displays
+     - Balance and transaction displays
+   - **Configuration & Settings:**
+     - Default currency preferences
+     - Exchange rate configurations
+     - Currency service initialization
+
+4. **Execute Systematically:** Start with backend currency service, then controllers, then frontend, then docs
+
+5. **Verify Thoroughly:** Use multiple verification commands:
+   - `grep -r "TFC" src/ --include="*.rs" --include="*.html" --include="*.js"`
+   - `grep -r "ThreeFold Credit" src/ --include="*.rs" --include="*.html" --include="*.js"`
+   - `grep -r "TF Credit" src/ --include="*.rs" --include="*.html" --include="*.js"`
+   - `grep -r "tfp" src/ --include="*.rs" --include="*.html" --include="*.js"`
+   - `grep -r "TFP" src/ --include="*.rs" --include="*.html" --include="*.js"`
+
+**Key Areas to Focus:**
+- Currency service and exchange rate logic
+- Wallet components and balance displays  
+- Transaction processing and records
+- Dashboard financial displays and charts
+- Marketplace pricing and payment flows
+- User settings and currency preferences
+- API responses with currency data
+- Database references and user data
+- Documentation and help text
+- Legal terms and agreements
+- Test files and mock data
+- Configuration files and settings
+
+**Implementation Strategy:**
+1. **Currency Service Foundation** - Update core currency logic and rates
+2. **Backend Controllers** - Update API endpoints and data processing  
+3. **Frontend Templates** - Update all user-facing currency displays
+4. **JavaScript Logic** - Update client-side currency handling
+5. **Documentation** - Update specs, docs, and legal terms
+6. **Configuration** - Update default settings and preferences
+7. **Testing** - Update test data and verify functionality
+
+**Critical Considerations:**
+- **Maintain 1 MC = 1 USD rate** - Ensure pricing calculations remain accurate
+- **User data migration** - Handle existing user balances and transaction history
+- **API compatibility** - Ensure external integrations continue to work
+- **Currency preferences** - Implement proper MC/USD/AED display options
+- **Backward compatibility** - Plan for any legacy TFC references
+
+**Expected File Updates:**
+- Currency service: `src/services/currency.rs` or similar
+- Controllers: `src/controllers/wallet.rs`, `src/controllers/dashboard.rs`
+- Models: `src/models/user.rs` (wallet/balance fields)
+- Frontend: All wallet, dashboard, and marketplace templates
+- JavaScript: Currency formatting and calculation logic
+- Tests: Update mock data and currency test cases
+- Docs: Update specs and user documentation
+- Legal: Update terms of service and agreements
+
+**Success Criteria:**
+- Zero remaining "TFC"/"ThreeFold Credit" references in codebase
+- All currency displays show "MC"/"Mycelium Credit"
+- Currency calculations maintain accuracy (1 MC = 1 USD)
+- Wallet and balance displays updated consistently
+- User preferences support MC/USD/AED display options
+- All financial flows (purchase, balance, transactions) work correctly
+- Documentation and legal terms updated
+- Tests pass with new currency terminology
+- No breaking changes to existing user data or API contracts
+
+**Verification Commands:**
+After implementation, run these verification commands to ensure complete migration:
+```bash
+grep -r "TFC" src/ --include="*.rs" --include="*.html" --include="*.js"          # Should return 0 results
+grep -r "ThreeFold Credit" src/ --include="*.rs" --include="*.html" --include="*.js"  # Should return 0 results
+grep -r "TF Credit" src/ --include="*.rs" --include="*.html" --include="*.js"   # Should return 0 results
+grep -r "\btfp\b" src/ --include="*.rs" --include="*.html" --include="*.js"     # Should return 0 results (word boundaries)
+grep -r "\bTFP\b" src/ --include="*.rs" --include="*.html" --include="*.js"     # Should return 0 results (word boundaries)
+
+# Verify successful replacements:
+grep -r "MC" src/ --include="*.rs" --include="*.html" --include="*.js"          # Should show currency references
+grep -r "Mycelium Credit" src/ --include="*.rs" --include="*.html" --include="*.js"  # Should show display text
+```
+
+**Important Notes:**
+- **Systematic Approach:** Follow the same methodical process used for Application Solutions → Agentic Apps
+- **Currency Service Priority:** Start with the core currency service to establish the foundation
+- **User Experience Focus:** Ensure all user-facing displays are consistent and clear
+- **Financial Accuracy:** Double-check all calculations and exchange rate logic
+- **Data Integrity:** Preserve existing user financial data during transition
+- **Testing Critical:** Financial systems require thorough testing before deployment
+
+**Expected Outcome:** Complete, consistent rebranding from "ThreeFold Credit (TFC)" to "Mycelium Credit (MC)" with proper currency system implementation, maintaining the same quality and thoroughness as previous rebrandings.
+
+---
+
+This currency rebranding represents a critical infrastructure change that affects the core financial operations of the marketplace. Systematic execution and thorough verification are essential to maintain system integrity and user trust.