refactor: migrate backend to Rust 1.97 and edition 2024

Unify the local, CI, release, and container toolchains on Rust 1.97.

Move update configuration, release caching, and event delivery into service-owned state, apply Edition 2024 idioms, and refresh repository ignore rules and documentation.

Co-authored-by: Codex <noreply@openai.com>

.github/workflows/_quality.yml

@@ -24,7 +24,6 @@ jobs:
       CARGO_TERM_COLOR: always
       CPR_TEST_DATABASE_URL: postgres://codex_proxy:codex_proxy@127.0.0.1:5432/codex_proxy
       CPR_TEST_REDIS_URL: redis://127.0.0.1:6379
-      RUSTFLAGS: -D warnings
     services:
       postgres:
         image: postgres:18-bookworm@sha256:d9c83446333daec3f0588cc709adb80c26090b7f9f0f7ec8d43c243385d79818
@@ -56,7 +55,7 @@ jobs:
           ref: ${{ inputs.ref }}
 
       - name: Setup Rust
-        uses: dtolnay/rust-toolchain@eac0f66a48bc4b70a10b9acd4c4e930f835d95ff # 1.95
+        uses: dtolnay/rust-toolchain@1a3a6d54512beeaffd394f8d516ca16f2c506a20 # 1.97
         with:
           components: rustfmt,clippy
 
@@ -71,7 +70,7 @@ jobs:
 
       - name: Rust clippy
         working-directory: backend
-        run: cargo clippy --all-targets --all-features --locked -- -D warnings
+        run: cargo clippy --all-targets --all-features --locked
 
       - name: Rust tests
         working-directory: backend

.github/workflows/release.yml

@@ -205,7 +205,7 @@ jobs:
             -v "$HOME/.cargo:/cargo" \
             -v "$PWD/..:/workspace" \
             -w /workspace/backend \
-            rust:1.95-bookworm@sha256:6258907abe69656e41cd992e0b705cdcfabcbbe3db374f92ed2d47121282d4a1 \
+            rust:1.97-bookworm@sha256:7d0723df719e7f213b69dc7c8c595985c3f4b060cfbee4f7bc0e347a86fe3b6a \
             cargo build --release --locked --target "${{ matrix.target }}" --bin codex-proxy-rs
           cp "target/${{ matrix.target }}/release/${{ matrix.binary }}" "../dist/binaries/${{ matrix.os }}-${{ matrix.arch }}/${{ matrix.binary }}"
         working-directory: backend
@@ -239,7 +239,7 @@ jobs:
           ref: ${{ needs.release-info.outputs.git_sha }}
 
       - name: Setup Rust
-        uses: dtolnay/rust-toolchain@eac0f66a48bc4b70a10b9acd4c4e930f835d95ff # 1.95
+        uses: dtolnay/rust-toolchain@1a3a6d54512beeaffd394f8d516ca16f2c506a20 # 1.97
         with:
           targets: ${{ matrix.target }}
 

.github/workflows/security-scan.yml

@@ -26,7 +26,7 @@ jobs:
           ref: ${{ github.event.pull_request.head.sha || github.sha }}
 
       - name: Setup Rust
-        uses: dtolnay/rust-toolchain@eac0f66a48bc4b70a10b9acd4c4e930f835d95ff # 1.95
+        uses: dtolnay/rust-toolchain@1a3a6d54512beeaffd394f8d516ca16f2c506a20 # 1.97
 
       - name: Cache Rust
         uses: Swatinem/rust-cache@c19371144df3bb44fab255c43d04cbc2ab54d1c4 # v2.9.1