fix: resolve media across libraries for video, metadata, and insights

The /video/generate and /image/metadata handlers assumed files live under
the resolved library only, which broke when a mobile client passed no
library (union mode) but the file lived in a non-primary library. Both
now fall back to scanning every configured library for an existing file.

InsightGenerator held a single base_path, so vision-model loads and
filename-date fallbacks failed for non-primary libraries. It now takes
Vec<Library> and probes each root in resolve_full_path.

/image/metadata responses now carry library_id/library_name so the
mobile viewer can surface which library a file belongs to.

Thumbnail generation at startup is now spawned on a background thread
so the HTTP server can accept traffic while large libraries backfill.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/ai/insight_generator.rs

@@ -16,6 +16,7 @@ use crate::database::{
     CalendarEventDao, DailySummaryDao, ExifDao, InsightDao, KnowledgeDao, LocationHistoryDao,
     SearchHistoryDao,
 };
+use crate::libraries::Library;
 use crate::memories::extract_date_from_filename;
 use crate::otel::global_tracer;
 use crate::tags::TagDao;
@@ -52,7 +53,7 @@ pub struct InsightGenerator {
     // Knowledge memory
     knowledge_dao: Arc<Mutex<Box<dyn KnowledgeDao>>>,
 
-    base_path: String,
+    libraries: Vec<Library>,
 }
 
 impl InsightGenerator {
@@ -67,7 +68,7 @@ impl InsightGenerator {
         search_dao: Arc<Mutex<Box<dyn SearchHistoryDao>>>,
         tag_dao: Arc<Mutex<Box<dyn TagDao>>>,
         knowledge_dao: Arc<Mutex<Box<dyn KnowledgeDao>>>,
-        base_path: String,
+        libraries: Vec<Library>,
     ) -> Self {
         Self {
             ollama,
@@ -80,10 +81,25 @@ impl InsightGenerator {
             search_dao,
             tag_dao,
             knowledge_dao,
-            base_path,
+            libraries,
         }
     }
 
+    /// Resolve `rel_path` against the configured libraries, returning the
+    /// first root under which the file exists. Insights may be generated
+    /// for any library — the generator itself doesn't know which — so we
+    /// probe each root rather than trust a single `base_path`.
+    fn resolve_full_path(&self, rel_path: &str) -> Option<std::path::PathBuf> {
+        use std::path::Path;
+        for lib in &self.libraries {
+            let candidate = Path::new(&lib.root_path).join(rel_path);
+            if candidate.exists() {
+                return Some(candidate);
+            }
+        }
+        None
+    }
+
     /// Extract contact name from file path
     /// e.g., "Sarah/img.jpeg" -> Some("Sarah")
     /// e.g., "img.jpeg" -> None
@@ -108,9 +124,13 @@ impl InsightGenerator {
     /// Resizes to max 1024px on longest edge to reduce context usage
     fn load_image_as_base64(&self, file_path: &str) -> Result<String> {
         use image::imageops::FilterType;
-        use std::path::Path;
 
-        let full_path = Path::new(&self.base_path).join(file_path);
+        let full_path = self.resolve_full_path(file_path).ok_or_else(|| {
+            anyhow::anyhow!(
+                "File '{}' not found under any configured library",
+                file_path
+            )
+        })?;
 
         log::debug!("Loading image for vision model: {:?}", full_path);
 
@@ -725,8 +745,7 @@ impl InsightGenerator {
             extract_date_from_filename(&file_path)
                 .map(|dt| dt.timestamp())
                 .or_else(|| {
-                    // Combine base_path with file_path to get full path
-                    let full_path = std::path::Path::new(&self.base_path).join(&file_path);
+                    let full_path = self.resolve_full_path(&file_path)?;
                     File::open(&full_path)
                         .and_then(|f| f.metadata())
                         .and_then(|m| m.created().or(m.modified()))
@@ -2455,7 +2474,7 @@ Return ONLY the summary, nothing else."#,
             extract_date_from_filename(&file_path)
                 .map(|dt| dt.timestamp())
                 .or_else(|| {
-                    let full_path = std::path::Path::new(&self.base_path).join(&file_path);
+                    let full_path = self.resolve_full_path(&file_path)?;
                     File::open(&full_path)
                         .and_then(|f| f.metadata())
                         .and_then(|m| m.created().or(m.modified()))