fix: auto-open video grid on camera/screenshare and harden CI supply chain (BUG-105, BUG-139)

BUG-105: checkVideoMode now auto-opens the video grid when any video
stream (local or remote camera/screenshare) becomes active. Previously
tiles were added to a hidden grid container.

BUG-139: All GitHub Actions pinned to commit SHAs instead of mutable
tags. Tool installs (govulncheck, tauri-typegen, cargo-audit) pinned
to specific versions instead of @latest.

.github/workflows/ci.yml

@@ -19,9 +19,9 @@ jobs:
       run:
         working-directory: Server/
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
 
-      - uses: actions/setup-go@v5
+      - uses: actions/setup-go@d35c59abb061a4a6fb18e82ac0862c26744d6ab5 # v5.5.0
         with:
           go-version: "1.25"
           cache-dependency-path: Server/go.sum
@@ -30,7 +30,7 @@ jobs:
         run: go build -o chatserver.exe -ldflags "-s -w" .
 
       - name: Go vulnerability check
-        run: go install golang.org/x/vuln/cmd/govulncheck@latest && govulncheck ./...
+        run: go install golang.org/x/vuln/cmd/govulncheck@v1.1.4 && govulncheck ./...
 
       - name: Run tests with race detection and coverage
         run: go test -race ./... -coverprofile=coverage.out -cover
@@ -40,14 +40,14 @@ jobs:
 
       - name: Upload Go coverage
         if: always()
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02 # v4.6.2
         with:
           name: go-coverage
           path: Server/coverage.out
           retention-days: 7
 
       - name: Lint
-        uses: golangci/golangci-lint-action@v9
+        uses: golangci/golangci-lint-action@4afd733a84b2f1a21f7c2e8a0e49adb3c0f2dbb6 # v9.0.0
         with:
           version: v2.11.3
           working-directory: Server/
@@ -59,9 +59,9 @@ jobs:
       run:
         working-directory: Client/tauri-client/
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
 
-      - uses: actions/setup-node@v4
+      - uses: actions/setup-node@49933ea5288caeca8642d1e84afbd3f7d6820020 # v4.4.0
         with:
           node-version: 20
           cache: npm
@@ -93,7 +93,7 @@ jobs:
 
       - name: Upload client coverage
         if: always()
-        uses: actions/upload-artifact@v4
+        uses: actions/upload-artifact@ea165f8d65b6e75b540449e92b4886f43607fa02 # v4.6.2
         with:
           name: client-coverage
           path: Client/tauri-client/coverage/
@@ -109,21 +109,21 @@ jobs:
       run:
         working-directory: Client/tauri-client/
     steps:
-      - uses: actions/checkout@v4
+      - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
 
-      - uses: actions/setup-node@v4
+      - uses: actions/setup-node@49933ea5288caeca8642d1e84afbd3f7d6820020 # v4.4.0
         with:
           node-version: 20
           cache: npm
           cache-dependency-path: Client/tauri-client/package-lock.json
 
       - name: Install Rust
-        uses: dtolnay/rust-toolchain@stable
+        uses: dtolnay/rust-toolchain@b3b07ba8b418998c39fb20f53e18c1f174353f26 # stable
         with:
           components: clippy
 
       - name: Rust cache
-        uses: swatinem/rust-cache@v2
+        uses: swatinem/rust-cache@9d47c6ad4b02e050fd481d890b2ea34778fd09d6 # v2.7.8
         with:
           workspaces: Client/tauri-client/src-tauri
 
@@ -131,7 +131,7 @@ jobs:
         run: npm ci
 
       - name: Install tauri-typegen
-        run: cargo install tauri-typegen --quiet
+        run: cargo install tauri-typegen@0.1.3 --quiet
 
       - name: Generate TypeScript IPC bindings
         working-directory: Client/tauri-client/
@@ -144,7 +144,7 @@ jobs:
       - name: Security audit (Rust dependencies)
         working-directory: Client/tauri-client/src-tauri/
         run: |
-          cargo install cargo-audit --quiet
+          cargo install cargo-audit@0.21.2 --quiet
           cargo audit
 
       - name: Build Tauri app