feat: KB Accelerator — convert KB articles into interactive flows

Full-stack implementation of the KB Accelerator feature that converts
static MSP knowledge base articles into interactive troubleshooting
and procedural flows using AI.

Backend:
- Migrations 054/055: kb_imports, kb_import_nodes tables + plan_limits KB columns
- SQLAlchemy models with relationships and self-referential node hierarchy
- Text extraction service (txt, paste, docx with structural metadata)
- AI conversion service with MSP-specialist prompts for both flow types
- 8 API endpoints: upload, get, list, convert, edit node, commit, delete, quota
- Tier-gated access via plan_limits (free: 3 lifetime, pro/team: unlimited)
- 8 integration tests covering upload, get/list, quota, commit, delete

Frontend:
- TypeScript types and API client for all KB Accelerator endpoints
- Multi-step wizard page: upload → processing → review → success
- Upload screen with paste/file tabs, drag-drop, target type selector
- Two-panel review screen with source highlighting and node cards
- Per-node actions: approve, edit, regenerate, insert, delete
- Confidence color indicators (green/amber/red)
- Sidebar navigation with Sparkles icon
- Code-split lazy-loaded route at /kb-accelerator

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

frontend/src/types/index.ts

@@ -73,3 +73,17 @@ export type {
   ContextMenuPosition,
   SuggestionMarker,
 } from './editor-ai'
+
+export type {
+  KBUploadTextRequest,
+  KBNodeEditRequest,
+  KBCommitRequest,
+  KBListParams,
+  KBImportNode,
+  KBUploadResponse,
+  KBImport,
+  KBImportSummary,
+  KBImportListResponse,
+  KBCommitResponse,
+  KBQuotaResponse,
+} from './kbAccelerator'

frontend/src/types/kbAccelerator.ts

@@ -0,0 +1,108 @@
+/**
+ * KB Accelerator types — converts KB articles into interactive flows.
+ */
+
+// ── Requests ──
+
+export interface KBUploadTextRequest {
+  content: string
+  title?: string
+  target_type?: 'troubleshooting' | 'procedural'
+}
+
+export interface KBNodeEditRequest {
+  operation: 'approve' | 'reject' | 'edit' | 'delete' | 'regenerate' | 'insert_after'
+  content?: Record<string, unknown>
+  guidance?: string
+}
+
+export interface KBCommitRequest {
+  name?: string
+  description?: string
+  category_id?: string
+}
+
+export interface KBListParams {
+  skip?: number
+  limit?: number
+  status?: string
+}
+
+// ── Responses ──
+
+export interface KBImportNode {
+  id: string
+  kb_import_id: string
+  node_order: number
+  node_type: string
+  content: Record<string, unknown>
+  parent_node_id: string | null
+  source_excerpt: string | null
+  confidence_score: number
+  user_edited: boolean
+  user_approved: boolean
+}
+
+export interface KBUploadResponse {
+  id: string
+  status: string
+  source_format: string
+}
+
+export interface KBImport {
+  id: string
+  account_id: string
+  created_by: string
+  source_filename: string | null
+  source_format: string
+  source_text: string
+  source_metadata: Record<string, unknown> | null
+  target_type: string
+  status: string
+  confidence_avg: number | null
+  error_message: string | null
+  processing_time_ms: number | null
+  ai_tokens_input: number | null
+  ai_tokens_output: number | null
+  tree_id: string | null
+  nodes: KBImportNode[]
+  created_at: string
+  updated_at: string
+}
+
+export interface KBImportSummary {
+  id: string
+  source_filename: string | null
+  source_format: string
+  target_type: string
+  status: string
+  confidence_avg: number | null
+  node_count: number
+  created_at: string
+}
+
+export interface KBImportListResponse {
+  items: KBImportSummary[]
+  total: number
+  skip: number
+  limit: number
+}
+
+export interface KBCommitResponse {
+  tree_id: string
+  import_id: string
+  tree_type: string
+}
+
+export interface KBQuotaResponse {
+  plan: string
+  kb_accelerator_enabled: boolean
+  lifetime_conversions_used: number
+  lifetime_conversions_limit: number | null
+  allowed_formats: string[]
+  detailed_analysis: boolean
+  conversational_refinement: boolean
+  step_library_matching: boolean
+  history_limit: number | null
+  can_convert: boolean
+}