Add langfuse and update logger (#952)

Co-authored-by: bytecraftii <bytecraftii@users.noreply.github.com>
Co-authored-by: Wendong-Fan <w3ndong.fan@gmail.com>

backend/.pre-commit-config.yaml

@@ -0,0 +1,87 @@
+ci:
+  # https://pre-commit.ci/#configuration
+  autofix_prs: true
+  autoupdate_commit_msg: '[pre-commit.ci] pre-commit suggestions'
+  autoupdate_schedule: monthly
+
+repos:
+  - repo: https://github.com/pre-commit/pre-commit-hooks
+    rev: v6.0.0
+    hooks:
+      - id: no-commit-to-branch
+        name: No commits to master
+      - id: end-of-file-fixer
+        name: End-of-file fixer
+      - name: mixed-line-ending
+        id: mixed-line-ending
+        args: [--fix, lf]
+      - id: trailing-whitespace
+        name: Remove trailing whitespaces
+      - id: check-toml
+        name: Check toml
+      - id: check-yaml
+        name: Check yaml
+
+  - repo: https://github.com/adrienverge/yamllint.git
+    rev: v1.37.1
+    hooks:
+      - id: yamllint
+        name: Lint yaml
+        args: [-d, '{extends: default, rules: {line-length: disable, document-start: disable, truthy: {level: error}, braces: {max-spaces-inside: 1}}}']
+
+  - repo: https://github.com/asottile/pyupgrade
+    rev: v3.21.0
+    hooks:
+      - id: pyupgrade
+        name: Upgrade Python syntax
+        args: [--py38-plus]
+
+  - repo: https://github.com/PyCQA/autoflake
+    rev: v2.3.1
+    hooks:
+      - id: autoflake
+        name: Remove unused imports and variables
+        args: [
+          --remove-all-unused-imports,
+          --remove-unused-variables,
+          --remove-duplicate-keys,
+          --ignore-init-module-imports,
+          --in-place,
+        ]
+
+  - repo: https://github.com/google/yapf
+    rev: v0.43.0
+    hooks:
+      - id: yapf
+        name: Format code
+        additional_dependencies: [toml]
+
+  - repo: https://github.com/pycqa/isort
+    rev: 7.0.0
+    hooks:
+      - id: isort
+        name: Sort imports
+
+  - repo: https://github.com/PyCQA/flake8
+    rev: 7.3.0
+    hooks:
+      - id: flake8
+        name: Check PEP8
+        additional_dependencies: [Flake8-pyproject]
+
+  - repo: https://github.com/astral-sh/ruff-pre-commit
+    rev: v0.14.3
+    hooks:
+      - id: ruff
+        name: Ruff formatting
+        args: [--fix, --exit-non-zero-on-fix]
+
+  - repo: https://github.com/executablebooks/mdformat
+    rev: 0.7.22
+    hooks:
+      - id: mdformat
+        name: Format Markdown
+        additional_dependencies:
+          - mdformat-gfm
+          - mdformat_frontmatter
+          - mdformat_footnote