build: replace faiss-cpu with lancedb for the AI vector store

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

pyproject.toml

@@ -42,7 +42,6 @@ dependencies = [
   "drf-spectacular~=0.28",
   "drf-spectacular-sidecar~=2026.5.1",
   "drf-writable-nested~=0.7.1",
-  "faiss-cpu>=1.10",
   "filelock~=3.29.0",
   "flower~=2.0.1",
   "gotenberg-client~=0.14.0",
@@ -50,6 +49,7 @@ dependencies = [
   "ijson>=3.2",
   "imap-tools~=1.13.0",
   "jinja2~=3.1.5",
+  "lancedb~=0.33.0",
   "langdetect~=1.0.9",
   "llama-index-core>=0.14.21",
   "llama-index-embeddings-huggingface>=0.6.1",
@@ -57,12 +57,12 @@ dependencies = [
   "llama-index-embeddings-openai-like>=0.2.2",
   "llama-index-llms-ollama>=0.9.1",
   "llama-index-llms-openai-like>=0.7.1",
-  "llama-index-vector-stores-faiss>=0.5.2",
   "nltk~=3.9.1",
   "ocrmypdf~=17.4.2",
   "openai>=2.32",
   "pathvalidate~=3.3.1",
   "pdf2image~=1.17.0",
+  "pyarrow>=16",
   "python-dateutil~=2.9.0",
   "python-dotenv~=1.2.1",
   "python-gnupg~=0.5.4",