feat: fix channel scanning bugs, add package tags, and kickstarters tab

Bug fixes:
- Fix channels not being scanned by paginating TDLib getChats (was only
  loading first batch, additional channels were unknown to TDLib)
- Add per-channel getChat pre-load as safety net before scanning
- Fix preview pictures not loading by checking previewData instead of
  previewMsgId for hasPreview flag
- Prevent previewMsgId from being set when preview download fails

Package Tags:
- Add tags Text[] column to Package with migration backfilling from
  channel categories
- Worker auto-inherits source channel category as initial tag
- Tag filter dropdown and Tags column in STL Files table
- Server actions for individual and bulk tag editing

Kickstarters Tab:
- New KickstarterHost, Kickstarter, and KickstarterPackage models
- Full CRUD with delivery status, payment status, host management
- Package linking (many-to-many with existing packages)
- Sidebar entry with Gift icon
- Table with search, filters, modal forms

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

worker/src/db/queries.ts

@@ -103,6 +103,7 @@ export interface CreatePackageInput {
   partCount: number;
   ingestionRunId: string;
   creator?: string | null;
+  tags?: string[];
   previewData?: Buffer | null;
   previewMsgId?: bigint | null;
   files: {
@@ -132,6 +133,7 @@ export async function createPackageWithFiles(input: CreatePackageInput) {
       fileCount: input.files.length,
       ingestionRunId: input.ingestionRunId,
       creator: input.creator ?? undefined,
+      tags: input.tags && input.tags.length > 0 ? input.tags : undefined,
       previewData: input.previewData ? new Uint8Array(input.previewData) : undefined,
       previewMsgId: input.previewMsgId ?? undefined,
       files: {