feat: add SQLite database layer with SQLModel

Add shared database infrastructure to clide core for use by both
the CLI and clide-web. SQLModel provides Pydantic-native models
that double as SQLAlchemy table definitions.

Models: Project, Session, UserPreference, ConnectionLog.

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

pyproject.toml

@@ -32,6 +32,8 @@ dependencies = [
     "rich>=13.0.0",
     "watchdog>=4.0.0",
     "wcwidth>=0.2.0",  # Required by vendored pyte
+    "sqlmodel>=0.0.16",
+    "aiosqlite>=0.20",
     # Tree-sitter for syntax highlighting
     "tree-sitter>=0.21.0",
     "tree-sitter-python>=0.21.0",