feat: add job worker and duplicate registration check

Job Worker System:
- Add polling-based job worker (max 2 concurrent processors)
- Create monitor_jobs records when videos are registered
- Link videos.job_id to monitor_jobs
- Fix type mismatches (i32 vs i64) for database IDs

Duplicate Registration:
- Check if video already exists before registering
- Return existing video info with already_exists: true
- Use canonical path for UUID computation

USER_DATA_ROOT Configuration:
- Add MOMENTRY_USER_DATA_ROOT environment variable
- UUID computed from relative path (username/filename)
- Ensures consistent UUIDs when data root changes

src/core/config.rs

@@ -60,6 +60,14 @@ pub static SERVER_PORT: Lazy<u16> = Lazy::new(|| {
 pub static REDIS_KEY_PREFIX: Lazy<String> =
     Lazy::new(|| env::var("MOMENTRY_REDIS_PREFIX").unwrap_or_else(|_| "momentry:".to_string()));
 
+/// User data root path (sftpgo data directory)
+/// This is the parent directory containing user directories like ./demo/, ./warren/, ./momentry/
+/// Example: /Users/accusys/momentry/var/sftpgo/data
+pub static USER_DATA_ROOT: Lazy<String> = Lazy::new(|| {
+    env::var("MOMENTRY_USER_DATA_ROOT")
+        .unwrap_or_else(|_| "/Users/accusys/momentry/var/sftpgo/data".to_string())
+});
+
 pub mod processor {
     use super::*;