initial: forecastlab_db read-only MCP server

Read-only MariaDB facade for Claude Code. 4 tools:
list_databases / list_tables / describe_table / query.

Safety:
- 3 databases allowlisted (forecastlab, weewx_db, homeassistant)
- SELECT / SHOW / DESCRIBE / EXPLAIN / WITH only
- multi-statement injection rejected
- 1000 row hard cap (200 default)
- prefers MCP_DB_RO_USER if set; falls back to DB_USER

Tested: 10/10 read-only guard cases pass.

.gitignore

@@ -0,0 +1,8 @@
+__pycache__/
+*.pyc
+*.pyo
+.venv/
+venv/
+.env
+*.log
+.DS_Store