ci: Tidy CI pipeline for readability and performance

Pipeline Modernisation:
- Update prefligit to prek (same project, renamed to avoid
  typosquatting)
- Replace custom rust-toolchain action with direct uvx rustup
  invocation
- Remove dependency on install scripts in favour of uvx tool
  execution
- Make sccache conditional on GH_APP_ID and GH_APP_PRIVATE_KEY
  availability

Workflow Restructuring:
- Rename workflows for improved clarity:
  * rust-checks.yml → ci-checks.yml (consolidates Rust + prek)
  * element.yml → deploy-element.yml
  * documentation.yml → deploy-docs.yml
  * release-image.yml → release-builds.yml (Docker + binaries)
  * mirror-images.yml → docker-mirror.yml
- Delete obsolete prefligit-checks.yml (merged into ci-checks.yml)
- Combine format and prek checks into single fast-checks job

Cache Strategy Improvements (release-builds.yml):
- Add restore-keys to Rust registry and cargo target caches
- Include Cargo.toml files in cargo-target cache key
- Consolidate separate apt-cache and apt-lib steps into single step
- Version APT cache with Dockerfile hash instead of static keys
- Add platform-specific Docker buildcache tags
- Simplify Rust registry paths (remove checkouts/src subdirs)

CI Execution Improvements:
- Add uv cache for faster uvx tool invocations (prek, rustup)
- Enable concurrency control with cancel-in-progress
- Fix BOM handling in pre-commit

Dependency Management:
- Add renovate.yml workflow for scheduled dependency checking
- Configure renovate.json to monitor .forgejo/ and .github/ dirs
- Group non-major GitHub Actions updates into single PRs
- Set PR limits: 3 concurrent, 2 per hour

.forgejo/workflows/documentation.yml

@@ -1,74 +0,0 @@
-name: Documentation
-
-on:
-  pull_request:
-  push:
-    branches:
-      - main
-    tags:
-      - "v*"
-  workflow_dispatch:
-
-concurrency:
-  group: "pages-${{ github.ref }}"
-  cancel-in-progress: true
-
-jobs:
-  docs:
-    name: Build and Deploy Documentation
-    runs-on: ubuntu-latest
-    if: secrets.CLOUDFLARE_API_TOKEN != ''
-
-    steps:
-      - name: Sync repository
-        uses: https://github.com/actions/checkout@v4
-        with:
-          persist-credentials: false
-          fetch-depth: 0
-
-      - name: Setup mdBook
-        uses: https://github.com/peaceiris/actions-mdbook@v2
-        with:
-          mdbook-version: "latest"
-
-      - name: Build mdbook
-        run: mdbook build
-
-      - name: Prepare static files for deployment
-        run: |
-          mkdir -p ./public/.well-known/matrix
-          mkdir -p ./public/.well-known/continuwuity
-          mkdir -p ./public/schema
-          # Copy the Matrix .well-known files
-          cp ./docs/static/server ./public/.well-known/matrix/server
-          cp ./docs/static/client ./public/.well-known/matrix/client
-          cp ./docs/static/client ./public/.well-known/matrix/support
-          cp ./docs/static/announcements.json ./public/.well-known/continuwuity/announcements
-          cp ./docs/static/announcements.schema.json ./public/schema/announcements.schema.json
-          # Copy the custom headers file
-          cp ./docs/static/_headers ./public/_headers
-          echo "Copied .well-known files and _headers to ./public"
-
-      - name: Setup Node.js
-        uses: https://github.com/actions/setup-node@v4
-        with:
-          node-version: 20
-
-      - name: Install dependencies
-        run: npm install --save-dev wrangler@latest
-
-      - name: Deploy to Cloudflare Pages (Production)
-        if: github.ref == 'refs/heads/main' && vars.CLOUDFLARE_PROJECT_NAME != ''
-        uses: https://github.com/cloudflare/wrangler-action@v3
-        with:
-          accountId: ${{ secrets.CLOUDFLARE_ACCOUNT_ID }}
-          apiToken: ${{ secrets.CLOUDFLARE_API_TOKEN }}
-          command: pages deploy ./public --branch="main" --commit-dirty=true --project-name="${{ vars.CLOUDFLARE_PROJECT_NAME }}"
-
-      - name: Deploy to Cloudflare Pages (Preview)
-        if: github.ref != 'refs/heads/main' && vars.CLOUDFLARE_PROJECT_NAME != ''
-        uses: https://github.com/cloudflare/wrangler-action@v3
-        with:
-          accountId: ${{ secrets.CLOUDFLARE_ACCOUNT_ID }}
-          apiToken: ${{ secrets.CLOUDFLARE_API_TOKEN }}
-          command: pages deploy ./public --branch="${{ github.head_ref || github.ref_name }}" --commit-dirty=true --project-name="${{ vars.CLOUDFLARE_PROJECT_NAME }}"