Add paddock briefing RSS backend spike

internal/store/migrations/003_news.sql

@@ -0,0 +1,24 @@
+CREATE TABLE IF NOT EXISTS news_sources (
+    source      TEXT    PRIMARY KEY,
+    name        TEXT    NOT NULL,
+    feed_url    TEXT    NOT NULL,
+    category    TEXT,
+    enabled     INTEGER NOT NULL DEFAULT 1,
+    fetched_at  INTEGER,
+    expires_at  INTEGER,
+    updated_at  INTEGER NOT NULL
+);
+
+CREATE TABLE IF NOT EXISTS news_items (
+    url          TEXT    PRIMARY KEY,
+    source      TEXT    NOT NULL,
+    title       TEXT    NOT NULL,
+    published_at INTEGER,
+    summary     TEXT,
+    category    TEXT,
+    fetched_at  INTEGER NOT NULL,
+    FOREIGN KEY (source) REFERENCES news_sources(source)
+);
+
+CREATE INDEX IF NOT EXISTS idx_news_items_published ON news_items (published_at DESC);
+CREATE INDEX IF NOT EXISTS idx_news_items_source_published ON news_items (source, published_at DESC);