feat: remove AI extensions, restructure settings, and add atomic voucher commits (#157)

Remove AI-dependent extensions (ai-chat, ai-categorization, receipt-ocr,
invoice-inbox) and their infrastructure (lib/ai/*, ai-consent, LangChain/
Anthropic/OpenAI deps) to simplify core and reduce bundle size.

Restructure monolithic settings page into dedicated sub-pages (company,
bookkeeping, invoicing, tax, banking, api, account, team, templates) with
shared layout and sidebar navigation.

Add atomic commit_journal_entry RPC so voucher number increment and status
update happen in a single transaction — prevents burned numbers on constraint
failures. Add continuity check report and voucher gap explanation tracking.

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

package.json

@@ -14,14 +14,7 @@
     "test": "vitest run"
   },
   "dependencies": {
-    "@anthropic-ai/sdk": "^0.72.1",
     "@hookform/resolvers": "^5.2.2",
-    "@langchain/anthropic": "^1.3.13",
-    "@langchain/core": "^1.1.18",
-    "@langchain/langgraph": "^1.2.0",
-    "@langchain/openai": "^1.2.4",
-    "@langfuse/core": "^4.6.1",
-    "@langfuse/langchain": "^4.6.1",
     "@radix-ui/react-checkbox": "^1.3.3",
     "@radix-ui/react-dialog": "^1.1.15",
     "@radix-ui/react-dropdown-menu": "^2.1.16",
@@ -46,7 +39,6 @@
     "fuse.js": "^7.1.0",
     "ics": "^3.8.1",
     "jszip": "^3.10.1",
-    "langchain": "^1.2.16",
     "lucide-react": "^0.563.0",
     "next": "16.1.5",
     "next-themes": "^0.4.6",