split: CI workflows, scripts, root tooling, and docs

Forgejo workflows (new), GitHub workflow tweaks, .gitignore/.vscode, root
package-lock, rustfmt.toml, scripts/* updates, docs/ updates including
data-flow / authentication / server-setup, CLAUDE.md and README updates.

.forgejo/workflows/check.yml

@@ -0,0 +1,35 @@
+name: Check
+
+on:
+  push:
+    branches: ["main"]
+  pull_request:
+    branches: ["main"]
+  workflow_dispatch:
+
+env:
+  CARGO_TERM_COLOR: always
+  RUSTFLAGS: "-Dwarnings"
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+
+    steps:
+      - uses: actions/checkout@v4
+        with:
+          fetch-depth: 0
+
+      - name: Setup Node.js environment
+        uses: actions/setup-node@v4
+        with:
+          node-version: "25.x"
+
+      - name: Setup Rust toolchain
+        uses: dtolnay/rust-toolchain@stable
+        with:
+          toolchain: "1.92.0"
+          components: clippy, rustfmt
+
+      - name: Lint & test
+        run: scripts/check.sh