ui(icons): unify mini-icon system for trees and shared chrome #472

Problem

Mini icons across Querya Desktop are almost entirely ad-hoc material.Icon(..., size: N) with no shared semantic registry or size tokens. Lucide / shadcn icon wrappers exist in vendored shadcn_flutter but are unused in lib/.

This causes the same UI roles to render differently by surface (native tree vs SDUI vs toolbars) and makes density / branding hard to keep consistent.

Scope

1. Shared icon layer

• Introduce a small semantic icon map (e.g. QueryaIcons / AppIcons) for tree + chrome roles: database, schema, table, view, function, sequence, index, folder, expand, error, loading affordance, etc.
• Centralize size tokens for mini roles (tree leaf / group / expand / toolbar / menu) instead of scattered 12|13|14|16|18.
• Keep Material as the glyph source for now (or explicitly decide Lucide) — avoid mixing families without a rule.

2. Connections / object trees

Align entity → icon across drivers and reuse one row chrome path where possible:

Key files:

• lib/features/connections/connections_panel_pg_tree.dart (_PgTreeRow)
• lib/features/connections/connections_panel_{mysql,sqlite,redis,mongo,extension}.dart
• lib/core/sdui/sdui_tree_builder.dart
• lib/features/connections/driver_icon.dart (PNG brands — keep)

3. Deduplicate connection-type icons

ConnectionType / driver → icon maps are copied in:

• connections_panel.dart
• new_connection_dialog.dart
• workspace_empty_hero.dart

Collapse to one source (ideally next to DriverIcon).

4. Broader chrome (light pass)

Apply the same size tokens to toolbars, title-bar menu leadings, toasts, and dialog headers so mini icons don’t jump between 15–24 without reason. Tab strip can stay text-only unless we deliberately add icons later.

Non-goals

• Full Lucide migration of the app
• Redesigning driver PNG brand marks
• Changing tree information architecture / labels

Acceptance criteria

• One semantic icon map used by PG/MySQL/SQLite/Mongo/Redis trees and SDUI string→icon mapping
• Shared size tokens for tree mini icons (leaf / group / expand) and documented toolbar/menu sizes
• Connection-type icon map defined once; panel / new-connection / empty hero consume it
• Same entity type shows the same glyph across native trees (and SDUI where the string maps to that entity)
• Error / empty affordances in trees consistently use an icon + message pattern
• No new Lucide/Material mix without an explicit comment/policy in the icon module

References

Post-0.4.11-b UI pass; related surfaces shipped under shell UX / connections panel.