feat(db): PostgreSQL 外部表与物化视图纳入树、动作与转储

[feigeCode]

Description

PostgreSQL connections only ever listed base tables: the listing SQL was hardcoded to c.relkind = 'r', so foreign tables ('f') and partitioned tables ('p') were invisible, and materialized views had no entry point at all (plain views were resolved through information_schema.views, which excludes matviews). A user who had already created foreign tables with Navicat could not see them in Navop.

This PR aligns the PostgreSQL object tree with Navicat and makes the actions correct, not just visible:

• Listing — list_tables / list_tables_view now accept 'r','p','f' and map relkind to an object type ('f' → ForeignTable, 'p'/'r' → Table). The object list "type" column shows Table / Partitioned Table / Foreign Table. New list_materialized_views reads pg_class (relkind = 'm') plus pg_get_viewdef, so materialized views no longer mix into plain views.
• Tree — new DbNodeType::{ForeignTable, MaterializedViewsFolder, MaterializedView}. Foreign, base and partitioned tables share one "Tables" folder (Navicat behavior); materialized views get their own folder, gated by a new supports_materialized_views capability flag (defaults to false, so MySQL and other drivers are unaffected).
• Actions — foreign tables and materialized views get their menu scoped per node type (Open / Rename / Truncate / Drop / Dump / Import / Export). Delete and rename dispatch by type to drop_foreign_table / rename_foreign_table / drop_materialized_view, so a plain DROP TABLE can never be sent to a foreign table. Actions without an implementation (design foreign table, copy table, foreign-table structure dump) are simply not registered, so no dead menu entries appear.
• Compare & dump — new TableObjectType::ForeignTable; is_ddl_comparable() keeps only plain tables, so foreign tables are automatically excluded from schema compare, data compare, ER diagram and whole-database DDL dump (data dump still works). resolve_sql_dump_target learns the new types so "Dump SQL File" no longer fails silently.
• Schema qualification — rename_foreign_table / drop_materialized_view now take a schema and emit schema-qualified names. The execution session never switches search_path, so on non-public schemas the previous DDL would have hit the wrong relation or errored out.

How to Test

# Unit / widget tests
cargo test -p db --lib          # 1305 passed
cargo test -p db_view --lib     # 703 passed, 1 ignored
cargo check --workspace --all-targets

# Real PostgreSQL integration test (skips unless the password env var is set)
ONETCLI_TEST_POSTGRES_PASSWORD=<password> cargo test -p db --test real_postgres   # 5 passed

The new crates/db/tests/real_databases/postgres/foreign_matview.rs creates a non-public schema with a real postgres_fdw foreign table (own foreign server + user mapping), a partitioned table and a materialized view, then asserts listing types, object-list types and tree placement, and actually executes rename/drop on the foreign table and drop on the materialized view. It also verifies list_views does not leak materialized views. The test cleans up after itself — no schema, foreign server or extension is left behind in the target database.

Manual smoke test: connect to a PostgreSQL database; the Tables folder now shows base, partitioned and foreign tables together with correct type labels, and a Materialized Views folder lists matviews with working Open Data / Dump / Delete.

Checklist

• I have read the CONTRIBUTING document and followed the guidelines.
• Reviewed the changes in this PR and confirmed AI generated code (If any) is accurate.
• Passed cargo run for story tests related to the changes. — not run: the story gallery is an interactive GUI; the touched views are covered by cargo test -p db_view instead, and the right-click menu click path has no automated regression yet.
• Tested macOS, Windows and Linux platforms performance (if the change is platform-specific) — not applicable, no platform-specific code.