fix(ci): properly configure uv environment for lint script

- Revert lint.sh to use direct commands (not uv run) since the script runs in uv environment
- Add 'uv sync' step to lint-backend.yml to install dependencies before running
- Commands in bash scripts run via 'uv run bash script.sh' already have access to the uv environment

Per uv documentation, when running 'uv run bash scripts/lint.sh', the environment is already set up,
so commands like mypy and ruff can be called directly without uv run prefix.

Related to CUR-29

🤖 Generated by Aygentic

Co-Authored-By: Aygentic <noreply@aygentic.com>

Author: amostt

.github/workflows/lint-backend.yml

@@ -24,5 +24,9 @@ jobs:
         with:
           version: "0.4.15"
           enable-cache: true
-      - run: uv run bash scripts/lint.sh
+      - name: Install dependencies
+        run: uv sync
+        working-directory: backend
+      - name: Run linters
+        run: uv run bash scripts/lint.sh
         working-directory: backend

backend/scripts/lint.sh

@@ -3,6 +3,6 @@
 set -e
 set -x
 
-uv run mypy app
-uv run ruff check app
-uv run ruff format app --check
+mypy app
+ruff check app
+ruff format app --check