[chore](trx-rs): add Gitea Actions CI pipeline

Introduce CI running on push to main and pull requests. Three jobs:
lint (rustfmt check + clippy with -D warnings), test (build and test the
workspace with --locked), and REUSE compliance. Installs the required
system libraries (opus, alsa, soapysdr) and caches the cargo registry
and target directory.

Assisted-By: Claude Code (claude-opus-4)
Claude-Session: https://claude.ai/code/session_01NFpGtGTWUEYXLwZeZs2RAV
Signed-off-by: Stan Grams <sjg@haxx.space>

.gitea/workflows/ci.yml

@@ -0,0 +1,98 @@
+# SPDX-FileCopyrightText: 2026 Stan Grams <sjg@haxx.space>
+#
+# SPDX-License-Identifier: GPL-2.0-or-later
+
+name: CI
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+env:
+  CARGO_TERM_COLOR: always
+
+jobs:
+  lint:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install system dependencies
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y --no-install-recommends \
+            build-essential pkg-config cmake \
+            libopus-dev libasound2-dev libsoapysdr-dev
+
+      - name: Set up Rust
+        run: |
+          if ! command -v rustup >/dev/null 2>&1; then
+            curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs \
+              | sh -s -- -y --profile minimal
+            echo "$HOME/.cargo/bin" >> "$GITHUB_PATH"
+          fi
+          rustup toolchain install stable --profile minimal \
+            --component rustfmt --component clippy
+          rustup default stable
+
+      - name: Cache cargo
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.cargo/registry
+            ~/.cargo/git
+            target
+          key: cargo-${{ runner.os }}-${{ hashFiles('**/Cargo.lock') }}
+          restore-keys: cargo-${{ runner.os }}-
+
+      - name: rustfmt
+        run: cargo fmt --all -- --check
+
+      - name: clippy
+        run: cargo clippy --workspace --all-targets --all-features -- -D warnings
+
+  test:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install system dependencies
+        run: |
+          sudo apt-get update
+          sudo apt-get install -y --no-install-recommends \
+            build-essential pkg-config cmake \
+            libopus-dev libasound2-dev libsoapysdr-dev
+
+      - name: Set up Rust
+        run: |
+          if ! command -v rustup >/dev/null 2>&1; then
+            curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs \
+              | sh -s -- -y --profile minimal
+            echo "$HOME/.cargo/bin" >> "$GITHUB_PATH"
+          fi
+          rustup toolchain install stable --profile minimal
+          rustup default stable
+
+      - name: Cache cargo
+        uses: actions/cache@v4
+        with:
+          path: |
+            ~/.cargo/registry
+            ~/.cargo/git
+            target
+          key: cargo-${{ runner.os }}-${{ hashFiles('**/Cargo.lock') }}
+          restore-keys: cargo-${{ runner.os }}-
+
+      - name: Build
+        run: cargo build --workspace --all-targets --locked
+
+      - name: Test
+        run: cargo test --workspace --locked
+
+  reuse:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - name: REUSE compliance
+        uses: fsfe/reuse-action@v5