feat: add logic_level and primary_use metadata to model groups

Schema: Added logic_level (INTEGER) and primary_use (TEXT) columns
to model_groups table with auto-migration for existing databases.

Seed: Three new default groups:
  heavy-logic  (level 9) — Complex Coding, Logic, Agents
  standard-pro (level 5) — General Assistant, Long Docs
  fast-flow    (level 2) — Classification, JSON, Basic Q&A

Admin API: INSERT/UPDATE handlers now accept and persist the new fields.
Dashboard: Table shows Level and Primary Use columns; form includes
both fields with appropriate inputs and placeholders.

internal/server/model_groups_admin.go

@@ -28,10 +28,10 @@ func (s *Server) handleCreateModelGroup(c *gin.Context) {
 	}
 
 	_, err := s.database.Exec(`
-		INSERT INTO model_groups (id, strategy, selector_model, targets, complexity_threshold, heuristic_rules)
-		VALUES (?, ?, ?, ?, ?, ?)`,
+		INSERT INTO model_groups (id, strategy, selector_model, targets, complexity_threshold, heuristic_rules, logic_level, primary_use)
+		VALUES (?, ?, ?, ?, ?, ?, ?, ?)`,
 		group.ID, group.Strategy, group.SelectorModel, group.Targets,
-		group.ComplexityThreshold, group.HeuristicRules)
+		group.ComplexityThreshold, group.HeuristicRules, group.LogicLevel, group.PrimaryUse)
 	if err != nil {
 		c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
 		return
@@ -50,10 +50,10 @@ func (s *Server) handleUpdateModelGroup(c *gin.Context) {
 	}
 
 	_, err := s.database.Exec(`
-		UPDATE model_groups SET strategy=?, selector_model=?, targets=?, complexity_threshold=?, heuristic_rules=?, updated_at=CURRENT_TIMESTAMP
+		UPDATE model_groups SET strategy=?, selector_model=?, targets=?, complexity_threshold=?, heuristic_rules=?, logic_level=?, primary_use=?, updated_at=CURRENT_TIMESTAMP
 		WHERE id=?`,
 		group.Strategy, group.SelectorModel, group.Targets,
-		group.ComplexityThreshold, group.HeuristicRules, id)
+		group.ComplexityThreshold, group.HeuristicRules, group.LogicLevel, group.PrimaryUse, id)
 	if err != nil {
 		c.JSON(http.StatusInternalServerError, gin.H{"error": err.Error()})
 		return