fix: address critical AI review issues

- Fix linuxdeploy AppImage extraction using --appimage-extract
- Remove 'has no column named' from duplicate column error handling
- Use strftime instead of datetime for created_at default format

.docker/Dockerfile.linux-amd64

@@ -26,9 +26,12 @@ RUN apt-get update -qq \
     && rm -rf /var/lib/apt/lists/*
 
 # Install linuxdeploy for AppImage bundling (required for Tauri 2.x)
-# Download linuxdeploy from the official repository and extract AppImage
-RUN curl -fsSL -L https://github.com/linuxdeploy/linuxdeploy/releases/download/continuous/linuxdeploy-x86_64.AppImage -o /usr/local/bin/linuxdeploy \
-    && chmod +x /usr/local/bin/linuxdeploy
+# Download linuxdeploy AppImage and extract to get the binary
+RUN curl -Ls https://github.com/tauri-apps/linuxdeploy/releases/download/continuous/linuxdeploy-x86_64.AppImage -o /tmp/linuxdeploy.AppImage \
+    && chmod +x /tmp/linuxdeploy.AppImage \
+    && /tmp/linuxdeploy.AppImage --appimage-extract \
+    && mv squashfs-root/usr/bin/linuxdeploy /usr/local/bin/ \
+    && rm -rf /tmp/linuxdeploy.AppImage squashfs-root
 
 RUN rustup target add x86_64-unknown-linux-gnu \
     && rustup component add rustfmt clippy

src-tauri/src/db/migrations.rs

@@ -197,7 +197,7 @@ pub fn run_migrations(conn: &Connection) -> anyhow::Result<()> {
         ),
         (
             "016_add_created_at",
-            "ALTER TABLE ai_providers ADD COLUMN created_at TEXT NOT NULL DEFAULT (datetime('now'))",
+            "ALTER TABLE ai_providers ADD COLUMN created_at TEXT NOT NULL DEFAULT (strftime('%Y-%m-%d %H:%M:%S', 'now'))",
         ),
     ];
 
@@ -218,12 +218,10 @@ pub fn run_migrations(conn: &Connection) -> anyhow::Result<()> {
                 || name.ends_with("_add_created_at")
             {
                 // Use execute for ALTER TABLE (SQLite only allows one statement per command)
-                // Skip error if column already exists
+                // Skip error if column already exists (SQLITE_ERROR with "duplicate column name")
                 if let Err(e) = conn.execute(sql, []) {
                     let err_str = e.to_string();
-                    if err_str.contains("duplicate column name")
-                        || err_str.contains("has no column named")
-                    {
+                    if err_str.contains("duplicate column name") {
                         tracing::info!("Column may already exist, skipping migration {name}: {e}");
                     } else {
                         return Err(e.into());