feat(phase9): frontend types + persistence wiring for llmTags

TranscriptEntry gains llmTags: string[]; TranscriptRow gains the
storage-shape llmTags: string. ContentTags type added. mapTranscriptRow
hydrates llmTags from the comma-joined column. saveTranscriptMeta
forwards llmTags through to update_transcript_meta_cmd, mirroring the
existing manualTags handling.

buildFrontmatter unions auto + manual + llm tags so exported markdown
surfaces every source in one tags: list.

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

src/lib/types/app.ts

@@ -180,6 +180,8 @@ export interface TranscriptDto {
   template: string;
   language: string;
   segmentsJson: string;
+  /** Phase 9. Comma-joined LLM-generated tags ("topic:foo", "intent:..."). */
+  llmTags: string;
 }
 
 export interface TranscriptEntry {
@@ -200,6 +202,13 @@ export interface TranscriptEntry {
   template: string;
   language: string;
   segments: Segment[];
+  /** Phase 9. AI-generated content tags ("topic:foo", "intent:..."). */
+  llmTags: string[];
+}
+
+export interface ContentTags {
+  topic: string;
+  intent: string;
 }
 
 export interface TranscriptWriteEntry extends Partial<TranscriptEntry> {
@@ -220,6 +229,9 @@ export interface TranscriptMetaPatch {
   template?: string;
   language?: string;
   segments?: Segment[];
+  /** Phase 9. Pass an array to set, an empty array to clear, or omit
+   *  the field to leave llm_tags unchanged. */
+  llmTags?: string[] | string;
 }
 
 /**