ci: cache pip wheels, npm deps, and embedded Python in release workflow

- Add pip and npm caching to build-windows and build-linux jobs
- Cache embedded Python zip and Windows wheels across runs
- Collapse per-dep pip download loop into a single resolver call

First run after this lands populates the caches; subsequent
release builds should drop from ~11min to ~3-5min.

.gitea/workflows/release.yml

@@ -105,6 +105,7 @@ jobs:
       - uses: actions/setup-node@v4
         with:
           node-version: '20'
+          cache: 'npm'
 
       - name: Build frontend
         run: npm ci && npm run build
@@ -112,6 +113,20 @@ jobs:
       - uses: actions/setup-python@v5
         with:
           python-version: '3.11'
+          cache: 'pip'
+          cache-dependency-path: pyproject.toml
+
+      - name: Cache embedded Python
+        uses: actions/cache@v4
+        with:
+          path: build/python-embed.zip
+          key: python-embed-3.11.9
+
+      - name: Cache Windows wheels
+        uses: actions/cache@v4
+        with:
+          path: build/win-wheels
+          key: win-wheels-${{ hashFiles('build-dist-windows.sh', 'pyproject.toml') }}
 
       - name: Install build tools
         run: sudo apt-get update && sudo apt-get install -y --no-install-recommends nsis zip
@@ -179,6 +194,7 @@ jobs:
       - uses: actions/setup-node@v4
         with:
           node-version: '20'
+          cache: 'npm'
 
       - name: Build frontend
         run: npm ci && npm run build
@@ -186,6 +202,8 @@ jobs:
       - uses: actions/setup-python@v5
         with:
           python-version: '3.11'
+          cache: 'pip'
+          cache-dependency-path: pyproject.toml
 
       - name: Build Linux distribution
         run: |