fix(smithery): Use container runtime pattern for config discovery

ADR-016: For container runtime deployment, Smithery does not auto-generate
the .well-known/mcp-config endpoint like it does for Python CLI runtime.

Changes:
- Remove [tool.smithery] from pyproject.toml (not used in container mode)
- Remove smithery_server.py (Python CLI runtime specific)
- Add .well-known/mcp-config endpoint to return JSON Schema config
- Add SmitheryConfigMiddleware to extract config from URL query params
- Use ContextVar to pass session config to tool handlers

The container runtime passes config as URL query parameters to /mcp:
  GET /mcp?nextcloud_url=...&username=...&app_password=...

Tested:
- All 164 unit tests passing
- Docker container builds successfully
- .well-known/mcp-config returns valid JSON Schema
- Health endpoints working

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

pyproject.toml

@@ -127,12 +127,10 @@ dev = [
 
 [project.scripts]
 nextcloud-mcp-server = "nextcloud_mcp_server.cli:run"
+smithery-main = "nextcloud_mcp_server.smithery_main:main"
 
 [[tool.uv.index]]
 name = "testpypi"
 url = "https://test.pypi.org/simple/"
 publish-url = "https://test.pypi.org/legacy/"
 explicit = true
-
-[tool.smithery]
-server = "nextcloud_mcp_server.smithery_server:create_server"