feat: stored procedures and functions

[datlechin]

Summary

Full stored procedure and function management for MySQL, MariaDB, PostgreSQL, and SQL Server (#693):

• Browse routines in a dedicated sidebar section with distinct icons (functions: purple, procedures: teal)
• Double-click to open routine detail view with Definition, Parameters, and DDL tabs
• Execute procedures/functions with parameter input dialog and SQL preview
• Create new procedures/functions from database-specific templates
• Drop with confirmation dialog
• View definition opens in query tab

Changes

New files (9):

• PluginRoutineInfo.swift / PluginRoutineParameterInfo.swift — plugin transfer types
• RoutineInfo.swift / RoutineParameterInfo.swift / RoutineDetailTab.swift — app models
• RoutineRowView.swift — sidebar row with type-based icons
• RoutineDetailView.swift + DataLoading extension — tabbed detail view (Definition/Parameters/DDL)
• ExecuteRoutineSheet.swift — execute dialog with parameter inputs and SQL preview

Plugin protocol (3 new methods + defaults):

• fetchRoutineParameters(routine:type:schema:) — parameter metadata
• createProcedureTemplate() / createFunctionTemplate() — creation templates

Database implementations:

DB	Parameters	Definition	Execute syntax
MySQL	INFORMATION_SCHEMA.PARAMETERS	SHOW CREATE PROCEDURE/FUNCTION	CALL / SELECT
PostgreSQL	pg_get_function_arguments(oid)	pg_get_functiondef(oid)	CALL / SELECT
MSSQL	INFORMATION_SCHEMA.PARAMETERS	OBJECT_DEFINITION	EXEC / SELECT

Tab system integration:

• QueryTab + EditorTabPayload + PersistedTab — added isRoutine and routineType fields
• MainEditorContentView — renders RoutineDetailView when showStructure && isRoutine

Sidebar enhancements:

• DoubleClickDetector on routine rows
• Context menu: View Definition, Execute..., Drop, Copy Name
• Section header context menu: Create Procedure..., Create Function...

No ABI version bump needed — all new protocol methods have default implementations.

Closes #693

Test plan

• MySQL: create procedure + function, verify sidebar listing, double-click opens detail view with 3 tabs
• MySQL: right-click Execute → parameter input dialog → SQL preview → opens in query tab
• MySQL: right-click Drop → confirmation → routine removed from sidebar
• MySQL: section header → Create Procedure/Function → template opens in query tab
• PostgreSQL: same flow, verify overloaded functions show one entry per name
• PostgreSQL: parameters parsed correctly from pg_get_function_arguments
• SQL Server: same flow, verify EXEC syntax in execute dialog
• SQLite/Redis/ClickHouse: no Routines section, no Create menu items
• Tab persistence: open routine detail, quit, reopen → tab restores
• View Definition with no tabs open → opens inline (not new window)
• Search filters routines alongside tables
• Collapse/expand Routines section persists across sessions