Add tags, export/import, and changelog features

- Tag editor in detail view with add/remove pill chips
- Tag filter chips in library view for filtering by tag
- Shared backup module for app list export/import (JSON v2)
- CLI export/import refactored to use shared module
- GUI export/import via file picker dialogs in hamburger menu
- GitHub release history enrichment for catalog apps
- Changelog preview in updates view with expandable rows
- DB migration v19 for catalog release_history column

src/core/github_enrichment.rs

@@ -265,6 +265,72 @@ pub fn enrich_app_release_info(
     Ok(remaining)
 }
 
+/// A GitHub release with body text for changelog display.
+#[derive(Debug, serde::Deserialize)]
+struct GitHubRelease {
+    tag_name: String,
+    published_at: Option<String>,
+    body: Option<String>,
+}
+
+/// Fetch up to 10 recent releases for a repo.
+fn fetch_recent_releases(owner: &str, repo: &str, token: &str) -> Result<(Vec<GitHubRelease>, u32), String> {
+    let url = format!("https://api.github.com/repos/{}/{}/releases?per_page=10", owner, repo);
+    let (body, remaining) = github_get(&url, token)?;
+    let releases: Vec<GitHubRelease> = serde_json::from_str(&body)
+        .map_err(|e| format!("Parse error: {}", e))?;
+    Ok((releases, remaining))
+}
+
+/// Enrich a catalog app with release history (version, date, description for last 10 releases).
+/// Only populates if the existing release_history is empty.
+pub fn enrich_app_release_history(
+    db: &Database,
+    app_id: i64,
+    owner: &str,
+    repo: &str,
+    token: &str,
+) -> Result<u32, String> {
+    // Check if release_history is already populated (from AppStream or prior enrichment)
+    if let Ok(Some(app)) = db.get_catalog_app(app_id) {
+        if app.release_history.as_ref().is_some_and(|h| !h.is_empty()) {
+            return Ok(u32::MAX); // already has data, skip
+        }
+    }
+
+    let (releases, remaining) = fetch_recent_releases(owner, repo, token)?;
+    if releases.is_empty() {
+        return Ok(remaining);
+    }
+
+    // Convert to the same JSON format used by AppStream: [{version, date, description}]
+    let history: Vec<serde_json::Value> = releases.iter().map(|r| {
+        let version = r.tag_name.strip_prefix('v')
+            .unwrap_or(&r.tag_name)
+            .to_string();
+        let date = r.published_at.as_deref()
+            .and_then(|d| d.split('T').next())
+            .unwrap_or("");
+        let mut obj = serde_json::json!({
+            "version": version,
+            "date": date,
+        });
+        if let Some(ref body) = r.body {
+            if !body.is_empty() {
+                obj["description"] = serde_json::Value::String(body.clone());
+            }
+        }
+        obj
+    }).collect();
+
+    let json = serde_json::to_string(&history)
+        .map_err(|e| format!("JSON error: {}", e))?;
+    db.update_catalog_app_release_history(app_id, &json)
+        .map_err(|e| format!("DB error: {}", e))?;
+
+    Ok(remaining)
+}
+
 /// Fetch and store the README for a catalog app.
 pub fn enrich_app_readme(
     db: &Database,
@@ -310,6 +376,9 @@ pub fn background_enrich_batch(
             Ok(remaining) => {
                 enriched += 1;
 
+                // Also fetch release history (changelog data)
+                let _ = enrich_app_release_history(db, app.id, owner, repo, token);
+
                 // Report progress
                 if let Ok((done, total)) = db.catalog_enrichment_progress() {
                     on_progress(done, total);