Treat Docker host gateway as local

When running Odysseus in Docker and connecting to a local LLM on the host machine (e.g. `llama.cpp` or `Ollama`), the standard endpoint `http://host.docker.internal` is used to breach the container network. 

Because `host.docker.internal` was missing from `_LOCAL_HOSTS`, Odysseus incorrectly treated local self-hosted models as cloud APIs. This triggered the fallback behavior where actual API-reported context limits were being ignored and overridden by hardcoded fallbacks in `KNOWN_CONTEXT_WINDOWS`.

**Changes**
- Added `"host.docker.internal"` to the `_LOCAL_HOSTS` whitelist in `src/model_context.py` so that Dockerized deployments correctly trust and respect the context limits of locally hosted models.

**Checks Ran**
- [x] Syntax check (`python -m py_compile src/model_context.py`)
- [x] Tested manually in Docker (`docker compose up -d --build`) on a Windows host using `llama-server`. The correct API context length is now correctly reported in the UI instead of falling back to the 131k hardcode.

src/model_context.py

@@ -14,7 +14,7 @@ import httpx
 
 logger = logging.getLogger(__name__)
 
-_LOCAL_HOSTS = {"localhost", "127.0.0.1", "0.0.0.0", "::1"}
+_LOCAL_HOSTS = {"localhost", "127.0.0.1", "0.0.0.0", "::1", "host.docker.internal"}
 _PRIVATE_PREFIXES = ("10.", "172.16.", "172.17.", "172.18.", "172.19.",
                      "172.20.", "172.21.", "172.22.", "172.23.", "172.24.",
                      "172.25.", "172.26.", "172.27.", "172.28.", "172.29.",