docs: create/update README.md for all 17 crates

Create 8 missing READMEs (config, ctrader-openapi, market-data, ml-data,
model_loader, risk-data, trading-data, training_uploader). Update 9 existing
READMEs to standard template format.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

crates/risk-data/README.md

@@ -0,0 +1,16 @@
+# risk-data
+
+Risk data repository for high-frequency trading risk management.
+
+## Key Types
+
+- `RiskDataConfig` — repository configuration
+- `VarRepository` — Value-at-Risk data storage
+- `LimitsRepository` — position and risk limit management
+- `ComplianceRepository` — compliance record storage
+
+## Usage
+
+```rust
+use risk_data::{RiskDataConfig, VarRepository};
+```