feat: nightly agentic pre-generation of memory reels

Implement end-to-end nightly pre-generation of memory reels with agentic
scripting that grounds narration in calendar, location, messages, and RAG.

Sections A-E from the plan:

A. Extract produce_reel pipeline core from run_reel_job with
   ScripterMode::Fast/Agentic and progress callbacks.

B. Agentic scripter: factor run_readonly_tool_loop from the insight
   generator, build read-only tool gate, prompt builder with GPS, and
   generate_script_agentic with fallback to fast path.

C. Precomputed reels ledger (SQLite table + DAO), GET /reels/precomputed
   handler with validity gate, GET /reels/by-key/{key}/video streaming,
   and normalize_library_key helper.

D. Nightly scheduler: spawn_pregen_scheduler with configurable hour,
   run_pregen_batch (day/week/month spans), pregen_one with dedup and
   disk-check, secs_until_next_run_hour time math.

E. user_ai_prefs passive mirror table + DAO for param capture in
   create_reel_handler and replay in the scheduler.

Also fixes resolve_library_param signature to take &[Library] and adds
resolve_library_param_state wrapper for AppState callers.

New files: migrations/2026-06-13-000000_add_precomputed_reels/,
  migrations/2026-06-13-000010_add_user_ai_prefs/,
  src/database/precomputed_reel_dao.rs,
  src/database/user_ai_prefs_dao.rs

src/handlers/video.rs

@@ -67,10 +67,11 @@ pub async fn generate_video(
     let context = extract_context_from_request(&request);
     let mut span = tracer.start_with_context("generate_video", &context);
 
-    let preferred_library = libraries::resolve_library_param(&app_state, body.library.as_deref())
-        .ok()
-        .flatten()
-        .unwrap_or_else(|| app_state.primary_library());
+    let preferred_library =
+        libraries::resolve_library_param_state(&app_state, body.library.as_deref())
+            .ok()
+            .flatten()
+            .unwrap_or_else(|| app_state.primary_library());
 
     // Try the resolved library first, then fall back to any other library
     // that actually contains the file — handles union-mode requests where