chore(packages): remove 4 dead zero-consumer packages

Pre-launch audit found 4 packages with zero workspace consumers
that were leftover from before the consolidation:

  - @mana/cards-database (1475 LOC)
    Pre-consolidation flashcard backend with its own Docker Compose
    and Drizzle config. Replaced by the cards module in the unified
    Mana app: apps/mana/apps/web/src/lib/modules/cards/. Now uses
    Dexie + mana-sync against mana_platform.

  - @mana/shared-api-client (1110 LOC)
    Generic Go-style {data, error} REST client. Only reference left
    was a string entry in shared-vite-config's noExternal list (not
    a real import).

  - @mana/shared-errors (1791 LOC)
    NestJS-coupled exception filter package from before the Hono
    migration. The Hono replacement (serviceErrorHandler in
    @mana/shared-hono) ships in a separate commit. Result<T,E> +
    ErrorCode enum bits had no consumers and weren't worth saving
    standalone — if a need emerges they can grow organically.

  - @mana/shared-splitscreen (694 LOC)
    Side-by-side panel layout components. No code consumers; only
    referenced from shared-vite-config noExternal and an old design
    doc. The unified Mana app uses its own workbench scenes for
    multi-pane layouts.

Verified zero code consumers via grep across .ts/.svelte/.json
before deletion. apps/api type-check stays at 0 errors after the
sweep, mana-auth tests still 19/19 passing.

Also clean packages/shared-vite-config/src/index.ts noExternal
list while we're here: drop the two deleted entries plus 8 ghost
packages (shared-feedback-ui/-service/-types, shared-help-ui/
-types/-content, shared-profile-ui, shared-subscription-ui) that
were referenced by name but never existed in packages/. List goes
from 22 → 12 entries.

Net: ~5070 LOC + workspace declarations removed.

Tracked as item #29 in docs/REFACTORING_AUDIT_2026_04.md.

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

packages/shared-vite-config/src/index.ts

@@ -16,23 +16,13 @@ export const MANA_SHARED_PACKAGES = [
 	'@mana/shared-tailwind',
 	'@mana/shared-theme',
 	'@mana/shared-theme-ui',
-	'@mana/shared-feedback-ui',
-	'@mana/shared-feedback-service',
-	'@mana/shared-feedback-types',
 	'@mana/shared-auth',
 	'@mana/shared-auth-ui',
 	'@mana/shared-branding',
-	'@mana/shared-subscription-ui',
-	'@mana/shared-profile-ui',
 	'@mana/shared-i18n',
-	'@mana/shared-api-client',
-	'@mana/shared-splitscreen',
 	'@mana/shared-utils',
 	'@mana/shared-tags',
 	'@mana/shared-stores',
-	'@mana/shared-help-types',
-	'@mana/shared-help-content',
-	'@mana/shared-help-ui',
 ] as const;
 
 /**