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>

src/components/layout/mobile-sidebar.tsx

@@ -10,6 +10,7 @@ import {
   Paintbrush,
   Gem,
   FileBox,
+  Gift,
   Send,
   ClipboardList,
   Building2,
@@ -22,7 +23,7 @@ import { cn } from "@/lib/utils";
 import { APP_NAME, NAV_ITEMS } from "@/lib/constants";
 import { SheetHeader, SheetTitle } from "@/components/ui/sheet";
 
-const icons = { LayoutDashboard, Cylinder, Droplets, Paintbrush, Gem, FileBox, Send, ClipboardList, Building2, MapPin, Settings, UserPlus };
+const icons = { LayoutDashboard, Cylinder, Droplets, Paintbrush, Gem, FileBox, Gift, Send, ClipboardList, Building2, MapPin, Settings, UserPlus };
 
 export function MobileSidebar() {
   const pathname = usePathname();

src/components/layout/sidebar.tsx

@@ -11,6 +11,7 @@ import {
   Paintbrush,
   Gem,
   FileBox,
+  Gift,
   Send,
   ClipboardList,
   Building2,
@@ -33,6 +34,7 @@ const icons = {
   Paintbrush,
   Gem,
   FileBox,
+  Gift,
   Send,
   ClipboardList,
   Building2,