feat: AI Act Decision Tree — Zwei-Achsen-Klassifikation (GPAI + High-Risk)

Interaktiver 12-Fragen-Entscheidungsbaum für die AI Act Klassifikation
auf zwei Achsen: High-Risk (Anhang III, Q1-Q7) und GPAI (Art. 51-56, Q8-Q12).
Deterministische Auswertung ohne LLM.

Backend (Go):
- Neue Structs: GPAIClassification, DecisionTreeAnswer, DecisionTreeResult
- Decision Tree Engine mit BuildDecisionTreeDefinition() und EvaluateDecisionTree()
- Store-Methoden für CRUD der Ergebnisse
- API-Endpoints: GET/POST /decision-tree, GET/DELETE /decision-tree/results
- 12 Unit Tests (alle bestanden)

Frontend (Next.js):
- DecisionTreeWizard: Wizard-UI mit Ja/Nein-Fragen, Dual-Progress-Bar, Ergebnis-Ansicht
- AI Act Page refactored: Tabs (Übersicht | Entscheidungsbaum | Ergebnisse)
- Proxy-Route für decision-tree Endpoints

Migration 083: ai_act_decision_tree_results Tabelle

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ai-compliance-sdk/internal/ucca/models.go

@@ -525,3 +525,73 @@ const (
 	ExportFormatJSON     ExportFormat = "json"
 	ExportFormatMarkdown ExportFormat = "md"
 )
+
+// ============================================================================
+// AI Act Decision Tree Types
+// ============================================================================
+
+// GPAICategory represents the GPAI classification result
+type GPAICategory string
+
+const (
+	GPAICategoryNone     GPAICategory = "none"
+	GPAICategoryStandard GPAICategory = "standard"
+	GPAICategorySystemic GPAICategory = "systemic"
+)
+
+// GPAIClassification represents the result of the GPAI axis evaluation
+type GPAIClassification struct {
+	IsGPAI             bool     `json:"is_gpai"`
+	IsSystemicRisk     bool     `json:"is_systemic_risk"`
+	Category           GPAICategory `json:"gpai_category"`
+	ApplicableArticles []string `json:"applicable_articles"`
+	Obligations        []string `json:"obligations"`
+}
+
+// DecisionTreeAnswer represents a user's answer to a decision tree question
+type DecisionTreeAnswer struct {
+	QuestionID string `json:"question_id"`
+	Value      bool   `json:"value"`
+	Note       string `json:"note,omitempty"`
+}
+
+// DecisionTreeQuestion represents a single question in the decision tree
+type DecisionTreeQuestion struct {
+	ID          string `json:"id"`
+	Axis        string `json:"axis"`        // "high_risk" or "gpai"
+	Question    string `json:"question"`
+	Description string `json:"description"` // Additional context
+	ArticleRef  string `json:"article_ref"` // e.g., "Art. 5", "Anhang III"
+	SkipIf      string `json:"skip_if,omitempty"` // Question ID — skip if that was answered "no"
+}
+
+// DecisionTreeDefinition represents the full decision tree structure for the frontend
+type DecisionTreeDefinition struct {
+	ID        string                 `json:"id"`
+	Name      string                 `json:"name"`
+	Version   string                 `json:"version"`
+	Questions []DecisionTreeQuestion `json:"questions"`
+}
+
+// DecisionTreeEvalRequest is the API request for evaluating the decision tree
+type DecisionTreeEvalRequest struct {
+	SystemName        string                        `json:"system_name"`
+	SystemDescription string                        `json:"system_description,omitempty"`
+	Answers           map[string]DecisionTreeAnswer  `json:"answers"`
+}
+
+// DecisionTreeResult represents the combined evaluation result
+type DecisionTreeResult struct {
+	ID                  uuid.UUID          `json:"id"`
+	TenantID            uuid.UUID          `json:"tenant_id"`
+	ProjectID           *uuid.UUID         `json:"project_id,omitempty"`
+	SystemName          string             `json:"system_name"`
+	SystemDescription   string             `json:"system_description,omitempty"`
+	Answers             map[string]DecisionTreeAnswer `json:"answers"`
+	HighRiskResult      AIActRiskLevel     `json:"high_risk_result"`
+	GPAIResult          GPAIClassification `json:"gpai_result"`
+	CombinedObligations []string           `json:"combined_obligations"`
+	ApplicableArticles  []string           `json:"applicable_articles"`
+	CreatedAt           time.Time          `json:"created_at"`
+	UpdatedAt           time.Time          `json:"updated_at"`
+}