feat: WP-0003 — RoutingPolicy (FR-2) and HTTP serve mode (FR-1)

FR-2 RoutingPolicy:
- RoutingPolicy + RoutingRule dataclasses in llm_connect/routing.py
- resolve(task_type, estimated_cost_per_1k=None) with cost-cap fallback
- Exported from llm_connect.__init__; contract doc at contracts/functional/routing-policy.md
- 11 tests covering rule match, cost-cap, fallback, unknown type, no-match

FR-1 HTTP serve mode:
- LLMServer in llm_connect/server.py (stdlib http.server, zero extra deps)
- POST /execute + GET /health; CLI via python -m llm_connect.server
- [server] optional-dep group added to pyproject.toml
- Contract doc at contracts/functional/server.md
- 9 tests: health, round-trip, 400/404/500 errors, config forwarding
- Added "mock" provider to factory for CLI default

All 101 tests pass.

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

llm_connect/__init__.py

@@ -33,6 +33,8 @@ from llm_connect.embedding_adapter import EmbeddingAdapter
 from llm_connect.embedding_openai import OpenAICompatibleEmbeddingAdapter
 from llm_connect.embedding_cache import EmbeddingCache
 from llm_connect.embedding_factory import create_embedding_adapter
+from llm_connect.routing import RoutingPolicy, RoutingRule
+from llm_connect.server import LLMServer
 from llm_connect.similarity import (
     cosine_similarity,
     similarity_matrix,
@@ -67,4 +69,7 @@ __all__ = [
     "cosine_similarity",
     "similarity_matrix",
     "find_similar_pairs",
+    "RoutingPolicy",
+    "RoutingRule",
+    "LLMServer",
 ]