refactor: replace fragmented theme system with unified ThemeEngine (#320)

* refactor: replace fragmented theme system with unified ThemeEngine

* fix: address review issues in theme engine migration

Author: datlechin

TablePro/Core/AI/InlineSuggestionManager.swift

@@ -310,7 +310,7 @@ final class InlineSuggestionManager {
         layer.allowsFontSubpixelQuantization = true
 
         // Use the editor's font and grey color for ghost appearance
-        let font = SQLEditorTheme.font
+        let font = ThemeEngine.shared.editorFonts.font
         let attrs: [NSAttributedString.Key: Any] = [
             .font: font,
             .foregroundColor: NSColor.tertiaryLabelColor

TablePro/Core/Plugins/PluginManager.swift

@@ -515,7 +515,7 @@ final class PluginManager {
         if let hex = PluginMetadataRegistry.shared.snapshot(forTypeId: databaseType.pluginTypeId)?.brandColorHex {
             return Color(hex: hex)
         }
-        return Theme.defaultDatabaseColor
+        return Color.gray
     }
 
     func supportsDatabaseSwitching(for databaseType: DatabaseType) -> Bool {

TablePro/Core/Services/Infrastructure/SettingsNotifications.swift

@@ -18,6 +18,10 @@ extension Notification.Name {
     static let editorSettingsDidChange = Notification.Name("editorSettingsDidChange")
 
     /// Posted when the system accessibility text size preference changes.
-    /// Observers should reload fonts via SQLEditorTheme.reloadFromSettings().
+    /// Observers should reload fonts via ThemeEngine.shared.reloadFontCaches().
     static let accessibilityTextSizeDidChange = Notification.Name("accessibilityTextSizeDidChange")
+
+    /// Posted when the active theme changes (colors, fonts, or entire theme switch).
+    /// Used by AppKit components that cannot observe @Observable directly.
+    static let themeDidChange = Notification.Name("themeDidChange")
 }

TablePro/Core/Vim/VimCursorManager.swift

@@ -96,7 +96,7 @@ final class VimCursorManager {
         }
 
         // Calculate character width from the editor font
-        let font = SQLEditorTheme.font
+        let font = ThemeEngine.shared.editorFonts.font
         let charWidth = (NSString(" ").size(withAttributes: [.font: font])).width
 
         guard charWidth > 0 else {
@@ -122,7 +122,7 @@ final class VimCursorManager {
             // Create new layer
             let layer = CALayer()
             layer.contentsScale = textView.window?.backingScaleFactor ?? 2.0
-            layer.backgroundColor = SQLEditorTheme.insertionPoint.withAlphaComponent(0.4).cgColor
+            layer.backgroundColor = ThemeEngine.shared.colors.editor.cursor.withAlphaComponent(0.4).cgColor
             layer.frame = frame
 
             // Add blink animation