feat(05-02): exa-search research integration

db/migrations/006_add_research_results.sql

@@ -0,0 +1,13 @@
+-- Store exercise research summaries and sources
+CREATE TABLE IF NOT EXISTS research_results (
+  id SERIAL PRIMARY KEY,
+  exercise_id INTEGER NOT NULL REFERENCES exercises(id) ON DELETE CASCADE,
+  query TEXT NOT NULL,
+  summary TEXT,
+  results JSONB NOT NULL DEFAULT '[]'::jsonb,
+  provider VARCHAR(50) NOT NULL DEFAULT 'exa',
+  created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP
+);
+
+CREATE INDEX IF NOT EXISTS idx_research_results_exercise_id ON research_results(exercise_id);
+CREATE INDEX IF NOT EXISTS idx_research_results_created_at ON research_results(created_at);