feat(phase9): migration v14 + storage and Tauri command extension for llm_tags

Adds llm_tags TEXT NOT NULL DEFAULT '' to the transcripts table via
new migration v14. SELECT statements + TranscriptRow + transcript_row_from
now carry the column. update_transcript_meta gains a sixth Option for
llm_tags following the existing COALESCE pattern; an
#[allow(too_many_arguments)] keeps clippy happy without inverting the
signature into a struct that would just shift the indirection.

The Tauri-side TranscriptDto + UpdateTranscriptMetaRequest + the
update_transcript_meta_cmd command pass llm_tags through unchanged.
Pre-existing manualTags persistence path now has a sibling for
llmTags ready for the frontend to call.

Phase 8 brittle test fix included: list_recent_completions_uses_local_day_boundary
was anchoring its "-2 days" UTC offset against the local-day spine,
which drifted across UTC midnight. Anchored to the local date directly
so it matches the spine regardless of clock.

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

crates/storage/src/migrations.rs

@@ -451,6 +451,18 @@ const MIGRATIONS: &[(i64, &str, &str)] = &[
             WHERE done_at IS NOT NULL;
         "#,
     ),
+    (
+        14,
+        "transcripts: llm_tags column for Phase 9 LLM content tags",
+        r#"
+        -- Phase 9 of the feature-complete roadmap. AI-generated content
+        -- tags (topic:* and intent:*) are stored alongside manual_tags as
+        -- a comma-joined string, mirroring how manual_tags persists. Pre-
+        -- existing rows default to empty string. The frontend chips loop
+        -- handles "" as "no tags".
+        ALTER TABLE transcripts ADD COLUMN llm_tags TEXT NOT NULL DEFAULT '';
+        "#,
+    ),
 ];
 
 /// Split SQL into individual statements, respecting BEGIN...END trigger blocks.
@@ -600,7 +612,7 @@ mod tests {
             .fetch_one(&pool)
             .await
             .unwrap();
-        assert_eq!(count, 13);
+        assert_eq!(count, 14);
 
         sqlx::query("INSERT INTO settings (key, value) VALUES ('test', 'value')")
             .execute(&pool)
@@ -619,7 +631,7 @@ mod tests {
             .fetch_one(&pool)
             .await
             .unwrap();
-        assert_eq!(count, 13);
+        assert_eq!(count, 14);
     }
 
     #[tokio::test]