feat: add ClickHouse database support

[datlechin]

Summary

Adds ClickHouse (columnar OLAP database) as a supported database engine in TablePro, closing #117.

• Connection: HTTP API on port 8123 via URLSession (no C bridge needed)
• Driver: Full DatabaseDriver protocol conformance using system.tables, system.columns, system.parts
• 39 files changed across driver, models, services, coordinators, views, tests, and docs

What works

• Connect, browse databases/tables, execute queries, view structure/DDL
• Data editing (INSERT/UPDATE/DELETE via async mutations)
• Export/import, filtering, autocomplete with ClickHouse dialect
• Database switching, approximate row counts, table metadata (engine, size)
• clickhouse:// and ch:// URL schemes

ClickHouse-specific behavior

• No foreign keys, no schemas, no transactions (no-op)
• Sorting key shown as primary index, data skipping indices listed
• toString() cast for LIKE on non-string columns, match() for regex
• Backslash string escaping (like MySQL), ? placeholders
• System databases (system, information_schema) marked as system items

Test plan

• Connect to a local ClickHouse instance on port 8123
• Browse databases and tables in sidebar
• Execute SELECT queries with pagination
• View table structure (columns, indexes, DDL)
• Edit data (insert/update/delete rows)
• Filter with LIKE, regex, boolean conditions
• Export table data (CSV, JSON, SQL)
• Switch databases via database switcher
• Verify ClickHouseColumnTypeTests pass
• Verify ClickHouseDialectTests pass
• Verify DatabaseTypeTests pass with new ClickHouse assertions

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