feat: add template selector to batch detail for CV generation

database.py

@@ -197,6 +197,8 @@ CREATE TABLE IF NOT EXISTS cv_batches (
     -- JSON array of positions extracted from the document
     -- [{job_title, num_positions, required_skills, required_years, required_certs, description}]
     positions JSONB DEFAULT '[]',
+    -- Selected Carbone template ID for CV generation
+    template_id TEXT,
     -- draft = still working, active = matching done, exported = CVs generated
     status VARCHAR(50) DEFAULT 'draft',
     created_at TIMESTAMPTZ DEFAULT NOW(),