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/model_loader/README.md

@@ -0,0 +1,17 @@
+# model_loader
+
+ML model loading and caching infrastructure.
+
+## Key Types
+
+- `AsyncModelLoader` — async model loading with LRU cache
+- `LoadedModelInfo` — loaded model metadata and weights
+- `ModelType` — re-exported from common (10 model variants)
+
+## Usage
+
+```rust
+use model_loader::AsyncModelLoader;
+let loader = AsyncModelLoader::new(cache_size);
+let model = loader.load("path/to/checkpoint").await?;
+```