Add per-source user_agent override for WAF-gated feeds

The Portugal News moved its RSS behind AWS WAF, which 405s Pete's honest
bot UA (confirmed: bot UA 0/6, browser UA 6/6 from the server IP). Add an
optional per-source user_agent that falls back to the default bot UA, and
set The Portugal News to a browser UA. Not load-related — 30-min polls and
the IP isn't banned.

internal/ingestion/parser.go

@@ -36,7 +36,7 @@ type FeedItem struct {
 	Source      string
 	DirectRoute string
 	Language    string // per-item <language> (or dc:language) when present; "" otherwise
-	PublishedAt int64 // unix seconds from RSS pubDate / Atom published (or updated as fallback); 0 if absent or unparseable
+	PublishedAt int64  // unix seconds from RSS pubDate / Atom published (or updated as fallback); 0 if absent or unparseable
 }
 
 var (
@@ -45,9 +45,9 @@ var (
 	imgSrcRe  = regexp.MustCompile(`(?i)<img[^>]+src=["']([^"']+)["']`)
 )
 
-
-// FetchFeed fetches and parses an RSS/Atom feed, returning items.
-func FetchFeed(feedURL string) ([]FeedItem, error) {
+// FetchFeed fetches and parses an RSS/Atom feed, returning items. ua overrides
+// the User-Agent header; pass "" to use Pete's honest default bot UA.
+func FetchFeed(feedURL, ua string) ([]FeedItem, error) {
 	ctx, cancel := context.WithTimeout(context.Background(), 30*time.Second)
 	defer cancel()
 
@@ -55,7 +55,10 @@ func FetchFeed(feedURL string) ([]FeedItem, error) {
 	if err != nil {
 		return nil, err
 	}
-	req.Header.Set("User-Agent", userAgent)
+	if ua == "" {
+		ua = userAgent
+	}
+	req.Header.Set("User-Agent", ua)
 	resp, err := feedClient.Do(req)
 	if err != nil {
 		return nil, err

internal/ingestion/poller.go

@@ -95,7 +95,7 @@ func (p *Poller) pollOnce(ctx context.Context, src config.SourceConfig) {
 }
 
 func (p *Poller) pollOnceWithErr(ctx context.Context, src config.SourceConfig) error {
-	items, err := FetchFeed(src.FeedURL)
+	items, err := FetchFeed(src.FeedURL, src.UserAgent)
 	if err != nil {
 		return err
 	}