infra: PostgreSQL audit schema for KB tracking

sql/01-audit-schema.sql

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+-- PostgreSQL Audit Schema for Knowledge Base Tracking
+-- Task 1.2: Create 3 tables with audit trail functionality
+
+-- Table 1: knowledge_base_updates
+-- Tracks all knowledge base updates with approval workflow
+CREATE TABLE IF NOT EXISTS knowledge_base_updates (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    ticket_id INTEGER NOT NULL,
+    problem_text TEXT NOT NULL,
+    kategorie VARCHAR(100),
+    lösung TEXT,
+    created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    approved_at TIMESTAMP,
+    executed_at TIMESTAMP,
+    status VARCHAR(50) NOT NULL DEFAULT 'PENDING',
+    freescout_note TEXT,
+    CONSTRAINT status_check CHECK (status IN ('PENDING', 'APPROVED', 'REJECTED', 'EXECUTED'))
+);
+
+-- Indexes for knowledge_base_updates
+CREATE INDEX idx_kbu_ticket_id ON knowledge_base_updates(ticket_id);
+CREATE INDEX idx_kbu_status ON knowledge_base_updates(status);
+CREATE INDEX idx_kbu_kategorie ON knowledge_base_updates(kategorie);
+
+-- Table 2: kb_feedback
+-- Stores user feedback on knowledge base entries
+CREATE TABLE IF NOT EXISTS kb_feedback (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    kb_entry_id VARCHAR(255) NOT NULL,
+    feedback VARCHAR(50) NOT NULL,
+    reason TEXT,
+    created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP,
+    CONSTRAINT feedback_check CHECK (feedback IN ('helpful', 'not_helpful'))
+);
+
+-- Index for kb_feedback
+CREATE INDEX idx_kbf_entry_id ON kb_feedback(kb_entry_id);
+
+-- Table 3: workflow_executions
+-- Tracks workflow execution history
+CREATE TABLE IF NOT EXISTS workflow_executions (
+    id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
+    workflow_name VARCHAR(255),
+    ticket_id INTEGER,
+    status VARCHAR(50),
+    error_message TEXT,
+    execution_time_ms INTEGER,
+    created_at TIMESTAMP NOT NULL DEFAULT CURRENT_TIMESTAMP
+);
+
+-- Indexes for workflow_executions
+CREATE INDEX idx_we_ticket_id ON workflow_executions(ticket_id);
+CREATE INDEX idx_we_workflow_name ON workflow_executions(workflow_name);
+
+-- Grant permissions to kb_user
+GRANT SELECT, INSERT, UPDATE, DELETE ON knowledge_base_updates TO kb_user;
+GRANT SELECT, INSERT, UPDATE, DELETE ON kb_feedback TO kb_user;
+GRANT SELECT, INSERT, UPDATE, DELETE ON workflow_executions TO kb_user;