docs: update TODO.md with Ollama provider completion

- Mark Ollama as completed provider implementation
- Add Ollama-specific feature checklist
- Update provider list in completed tasks

TODO.md

@@ -5,7 +5,7 @@
 - [x] Database schema & migrations (hardcoded in `db.go`)
 - [x] Configuration loader (Viper)
 - [x] Auth Middleware (scoped to `/v1`)
-- [x] Basic Provider implementations (OpenAI, Gemini, DeepSeek, Grok)
+- [x] Basic Provider implementations (OpenAI, Gemini, DeepSeek, Grok, Ollama)
 - [x] Streaming Support (SSE & Gemini custom streaming)
 - [x] Archive Rust files to `rust` branch
 - [x] Clean root and set Go version as `main`
@@ -47,6 +47,12 @@
 - [x] Multimodal support
 - [x] Accurate usage parsing (via OpenAI helper)
 
+### Ollama Provider
+- [x] OpenAI-compatible API integration
+- [x] Streaming support
+- [x] Model pattern detection for routing
+- [x] Zero cost calculation (local/free models)
+
 ## Infrastructure & Middleware
 - [ ] Implement Rate Limiting (`golang.org/x/time/rate`)
 - [ ] Implement Circuit Breaker (`github.com/sony/gobreaker`)