Fix agentic reel audit issues: midnight bug, DAO wiring, dead code, DST timezone, validation

Blocking fixes:
- secs_until_next_run_hour: same-hour now returns 0 instead of 24h
- capture_prefs: called at both handler return points, never fails request
- capture_prefs: resolves library param, upserts to user_ai_prefs via DAO
- Scheduler: uses AppState DAOs instead of separate connections
- Pregen dedup: uses resolved library param instead of hardcoded 'all'
- run_readonly_tool_loop: added #[allow(dead_code)] (used in main.rs only)
- run_readonly_tool_loop: removed dead messages.push() call
- InsightGenerator: added exif_dao() getter for scheduler reuse

Medium fixes:
- Input validation: run_hour clamped 0-23, week_dow clamped 0-6
- DST-sensitive timezone: fixed_tz_offset() with env var config

Low fixes:
- Documented REEL_PREGEN_MAX_TOOL_ITERS and REEL_PREGEN_TZ_FIXED_MINUTES
- Removed dead test_app_state function and unused imports

Also fix: UpsertUserAiPrefs import path, chrono::Local::with_ymd_and_hms
requires TimeZone trait + .single(), unwrap_or_else closure simplification

.env.example

@@ -150,8 +150,13 @@ SEARCH_RAG_RERANK=0
 # Timezone offset in minutes from UTC (e.g., -480 = PST). Defaults to
 # the server's local timezone.
 # REEL_PREGEN_TZ_OFFSET_MINUTES=
+# Fixed timezone offset — overrides auto-detect to avoid DST shifts.
+# When set, both the DB fallback and env fallback use this value.
+# REEL_PREGEN_TZ_FIXED_MINUTES=-480
 # Voice ID for narration (e.g., "grandma"). Falls back to the value
 # stored in the user_ai_prefs DB row when set.
 # REEL_PREGEN_VOICE=
 # Library filter: a library id (e.g. "1") or "all" for every library.
 # REEL_PREGEN_LIBRARY=all
+# Max agentic tool iterations for pre-gen scripter. Default 8.
+# REEL_PREGEN_MAX_TOOL_ITERS=8