feat: add conversation persistence and context management layer

- SQLAlchemy async database layer (SQLite dev, PostgreSQL prod)
- Conversation and Message models with UUID primary keys
- Token counting utilities using litellm
- Context summarization at 80% token threshold
- REST API endpoints for multi-turn conversations
- 19 conversation tests, 6 token tests (176 total passing)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

webber-api/pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "webber-api"
-version = "0.3.4"
+version = "0.4.0"
 description = "Webber API - Multi-Agent AI Development Server"
 authors = [
     {name = "jpmschweitzer"}
@@ -27,7 +27,7 @@ include = ["src*"]
 testpaths = ["tests"]
 python_files = ["test_*.py"]
 python_functions = ["test_*"]
-addopts = "-v --strict-markers"
+addopts = "-q --strict-markers --tb=short"
 markers = [
     "integration: marks tests as integration tests (require Ollama to be running)",
     "e2e: marks tests as end-to-end tests (require API server to be running)",