Add Twitter video support and use sql.Null[T] for nullable columns

- Store Twitter video URLs in embed_video_url column instead of downloading
- Play videos directly from Twitter's CDN in <video> element
- Fix Twitter API parsing (content_type/url fields)
- Strip t.co URLs from tweet text descriptions
- Use sql.Null[T] generic type for nullable DB columns
- Add Nullable[T] and Ptr[T] helper functions
- Add play indicator overlay for video items in grid
- Add migration for embed_video_url column

internal/embed/detect.go

@@ -7,6 +7,7 @@ import (
 	"net/http"
 	"net/url"
 	"regexp"
+	"strings"
 	"time"
 )
 
@@ -27,12 +28,14 @@ type VideoInfo struct {
 	Description  string
 	ThumbnailURL string
 	EmbedHTML    string
+	VideoURL     string // Direct video URL (for Twitter videos)
 }
 
 var (
 	youtubeRegex = regexp.MustCompile(`(?:youtube\.com/(?:watch\?v=|embed/|v/|shorts/)|youtu\.be/)([a-zA-Z0-9_-]{11})`)
 	vimeoRegex   = regexp.MustCompile(`(?:vimeo\.com/(?:video/)?|player\.vimeo\.com/video/)(\d+)`)
 	twitterRegex = regexp.MustCompile(`(?:twitter\.com|x\.com)/([^/]+)/status/(\d+)`)
+	tcoRegex     = regexp.MustCompile(`\s*https://t\.co/\S+`)
 )
 
 // Detect checks if a URL is a YouTube, Vimeo, or Twitter/X post and returns its info.
@@ -121,6 +124,13 @@ type twitterSyndicationResponse struct {
 	MediaDetails []struct {
 		MediaURLHTTPS string `json:"media_url_https"`
 		Type          string `json:"type"`
+		VideoInfo     struct {
+			Variants []struct {
+				ContentType string `json:"content_type"`
+				URL         string `json:"url"`
+				Bitrate     int    `json:"bitrate,omitempty"`
+			} `json:"variants"`
+		} `json:"video_info"`
 	} `json:"mediaDetails"`
 	Video struct {
 		Poster string `json:"poster"`
@@ -152,13 +162,26 @@ func fetchTwitter(ctx context.Context, tweetID string, originalURL string) (*Vid
 		return nil, fmt.Errorf("twitter syndication decode: %w", err)
 	}
 
-	// Find thumbnail - prefer photos, then video poster
-	var thumbnailURL string
+	// Find thumbnail and video URL from media
+	var thumbnailURL, videoURL string
 	if len(tweet.Photos) > 0 {
 		thumbnailURL = tweet.Photos[0].URL
 	} else if len(tweet.MediaDetails) > 0 {
-		thumbnailURL = tweet.MediaDetails[0].MediaURLHTTPS
-	} else if tweet.Video.Poster != "" {
+		media := tweet.MediaDetails[0]
+		thumbnailURL = media.MediaURLHTTPS
+
+		// Extract video URL - find highest bitrate MP4
+		if media.Type == "video" || media.Type == "animated_gif" {
+			var bestBitrate int
+			for _, v := range media.VideoInfo.Variants {
+				if v.ContentType == "video/mp4" && v.Bitrate >= bestBitrate {
+					bestBitrate = v.Bitrate
+					videoURL = v.URL
+				}
+			}
+		}
+	}
+	if thumbnailURL == "" && tweet.Video.Poster != "" {
 		thumbnailURL = tweet.Video.Poster
 	}
 
@@ -173,12 +196,17 @@ func fetchTwitter(ctx context.Context, tweetID string, originalURL string) (*Vid
 		title = fmt.Sprintf("%s (@%s)", tweet.User.Name, tweet.User.ScreenName)
 	}
 
+	// Clean up tweet text - remove trailing t.co URLs
+	description := tcoRegex.ReplaceAllString(tweet.Text, "")
+	description = strings.TrimSpace(description)
+
 	return &VideoInfo{
 		Provider:     ProviderTwitter,
 		VideoID:      tweetID,
 		Title:        title,
-		Description:  tweet.Text,
+		Description:  description,
 		ThumbnailURL: thumbnailURL,
+		VideoURL:     videoURL,
 		EmbedHTML:    embedHTML,
 	}, nil
 }