feat: add CockroachDB database support

[datlechin]

Summary

Closes #114

Adds CockroachDB database support to TablePro. CockroachDB is PostgreSQL wire-compatible, so this leverages the existing LibPQ connector with CockroachDB-specific extensions.

What's included

• CockroachDBDriver — Full driver implementation using libpq (PostgreSQL wire protocol), with CockroachDB-specific queries for:
  • Real index browsing via pg_index/pg_class (unlike Redshift's DISTKEY/SORTKEY)
  • Approximate row counts via crdb_internal.table_row_statistics
  • Table size via crdb_internal.table_span_stats with pg_total_relation_size() fallback
  • System databases: system, defaultdb
  • Schema switching, DDL generation, view definitions
  • Auto-reconnect on connection loss
• Icon asset — Placeholder SVG icon for CockroachDB connections
• Default port: 26257
• URL scheme: cockroachdb://
• Schema editing support (ALTER TABLE — unlike Redshift)

Integration points (already in main)

All switch statement integrations were included in a prior commit. This PR adds the driver implementation and icon asset that were missing.

Test plan

• Create a CockroachDB connection with host/port/credentials
• Verify connection test succeeds
• Browse tables, columns, indexes
• Execute queries
• Verify schema switching works
• Test cockroachdb:// URL import
• Verify icon displays in sidebar and connection form

[Copilot]

Copilot encountered an error and was unable to review this pull request. You can try again by re-requesting a review.