Add web search knowledge base, message tagging, and word-memory tip topics

Introduces websearch.py (Tavily) + knowledge.py to ground chat responses
in search results, tagging.py to tag user and assistant messages via LLM
and pick related topics for the Discord useless-tips job, and
word_memory.py to track recent conversation nouns (surfaced in the new
WordPool.vue sidebar) used to pick tip topics close to a related tag.

backend/uv.lock

@@ -727,6 +727,15 @@ wheels = [
     { url = "https://files.pythonhosted.org/packages/cb/b1/3846dd7f199d53cb17f49cba7e651e9ce294d8497c8c150530ed11865bb8/iniconfig-2.3.0-py3-none-any.whl", hash = "sha256:f631c04d2c48c52b84d0d0549c99ff3859c98df65b3101406327ecc7d53fbf12", size = 7484, upload-time = "2025-10-18T21:55:41.639Z" },
 ]
 
+[[package]]
+name = "janome"
+version = "0.5.0"
+source = { registry = "https://pypi.org/simple" }
+sdist = { url = "https://files.pythonhosted.org/packages/08/4e/dc2b1a89a4ffafbf9bf49c8e11f69e28ba8b3ef81d11afe6e9f96caee6cc/Janome-0.5.0.tar.gz", hash = "sha256:ce4a3ed7a4635c2f80139639327d5b1e0381858ad74a3c4a61e8cc83f820400e", size = 18829020, upload-time = "2023-07-01T10:53:09.161Z" }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/73/7d/70f4069f4bbf0fca023e82a1fbbade6f5216365d4fe259fee1950723eca5/Janome-0.5.0-py2.py3-none-any.whl", hash = "sha256:d098670394a77881ce2f6b7d696c0ea5ff74c0c8cf74a8a882159ec82c0e6dc7", size = 19654103, upload-time = "2023-07-01T10:52:58.572Z" },
+]
+
 [[package]]
 name = "jinja2"
 version = "3.1.6"
@@ -1114,6 +1123,7 @@ dependencies = [
     { name = "fastapi" },
     { name = "httpx" },
     { name = "huggingface-hub" },
+    { name = "janome" },
     { name = "litellm" },
     { name = "nvidia-ml-py" },
     { name = "psutil" },
@@ -1140,6 +1150,7 @@ requires-dist = [
     { name = "httpx", specifier = ">=0.28.1" },
     { name = "httpx", marker = "extra == 'dev'", specifier = ">=0.27.0" },
     { name = "huggingface-hub", specifier = ">=1.17.0" },
+    { name = "janome", specifier = ">=0.5.0" },
     { name = "litellm", specifier = ">=1.40.0" },
     { name = "nvidia-ml-py", specifier = ">=13.610.43" },
     { name = "psutil", specifier = ">=7.2.2" },