Fix review findings: secrets in snapshots, URL spoofing, migration data loss

Adversarial review of the branch produced findings across four areas.
This addresses them, plus the Windows CI environment.

Secrets. commit_container_snapshot baked the container's full env into
the per-project snapshot image, so the shared OAuth token — and the AWS
keys, git token and gateway master key — outlived revocation and were
readable via docker inspect. Verified against Engine 29.6 that a commit
body's config merges over the container's: keys cannot be dropped but
can be overwritten, so all of them now commit as KEY=. clear_claude_token
additionally rewrites images from earlier builds and reports honestly
when a tag could not be rewritten.

The recommendation to move the token out of env entirely was not taken,
with reasoning: apiKeyHelper is a different auth method that outranks
CLAUDE_CODE_OAUTH_TOKEN rather than a transport for it, and no
file-based delivery exists. The durable exposure — the image — is what
is closed here. Separately noted, not fixed: entrypoint.sh captures the
token into the scheduler's .env inside the persisted volume.

URL spoofing. Three call sites reached openUrl with container-controlled
strings, one of which the review missed (the WebLinksAddon handler).
The sign-in URL was scraped from container output with a longest-match
tie-break and no userinfo check, so claude.ai@evil.tld rendered as
"claude.ai…" in a truncating element. There is now one sanitizer in
front of every sink — scheme allowlist, no userinfo, C0/C1 and quote
rejection, host allowlist for the sign-in case, first-match — and the
origin renders un-truncated. The toast is keyed so a changed URL
remounts, closing a bait-and-switch where the user read one URL and
clicked another.

Migration. The rollback pin was best-effort: a tag failure was logged
and the migration continued past remove_container, after which the
final commit overwrote the only copy of the old system layer. It now
aborts before anything destructive and reads the tag back. /var was
destroyed while the ordinary recreate path preserves it — making the
"safe" alternative to Reset more destructive than Reset's alternative;
data-bearing subtrees are now detected and disclosed in the pre-flight
rather than copied, since tarring a live database onto a different
base's packages is a corruption risk. resume_migration now verifies the
migration-state label instead of reporting success for a container that
never swapped. dismiss actually resolves the record rather than leaving
the feature permanently refusing to migrate. Start and Reset are guarded
while a migration is live.

Lifecycle. The gateway no longer publishes on 0.0.0.0 — bind address and
advertised URL are derived together so they cannot drift. Disabling it
now stops it. App exit runs teardown concurrently under a budget with a
visible shutting-down state instead of blocking for minutes. Auto-starts
retry when Docker is not up yet, and the polling-recovery path now
reconciles, so interrupted migrations are still recovered. Auth-bridge
forwards are capped, closing a container-driven fd exhaustion.

Windows CI. build-windows failed on this branch with "linker link.exe
not found". The runner had no MSVC build tools and the workflow assumed
a hand-provisioned machine, so a bare runner registers, accepts jobs and
fails at link time after downloading the whole crate graph. The job now
installs the VC++ workload when vswhere cannot find it, matching how it
already conditionally installs Rust and Node.

192 Rust tests, 274 frontend tests, both builds clean, zero warnings.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

.gitea/workflows/build-app.yml

@@ -357,6 +357,38 @@ jobs:
           (Get-Content app/src-tauri/Cargo.toml) -replace '^version = ".*?"', "version = `"$version`"" | Set-Content app/src-tauri/Cargo.toml
           Write-Host "Patched version to $version"
 
+      - name: Install MSVC C++ build tools
+        shell: cmd
+        run: |
+          rem Tauri links with MSVC, so rustc needs link.exe and the Windows SDK.
+          rem This job previously assumed a hand-provisioned runner; a runner
+          rem without them registers fine, accepts windows-latest jobs, and then
+          rem fails at link time with "linker `link.exe` not found" after having
+          rem already downloaded the whole crate graph.
+          rem
+          rem rustc locates MSVC through vswhere/the registry rather than PATH,
+          rem so installing is sufficient — no dev-shell activation needed here.
+          set "VSWHERE=%ProgramFiles(x86)%\Microsoft Visual Studio\Installer\vswhere.exe"
+          if exist "%VSWHERE%" (
+            "%VSWHERE%" -latest -products * -requires Microsoft.VisualStudio.Component.VC.Tools.x86.x64 -property installationPath > "%TEMP%\vcpath.txt" 2>nul
+            for /f "usebackq delims=" %%i in ("%TEMP%\vcpath.txt") do set "VCPATH=%%i"
+          )
+          if defined VCPATH (
+            echo MSVC build tools already present at %VCPATH%
+          ) else (
+            echo MSVC build tools not found - installing Visual Studio Build Tools
+            curl -fSL -o "%TEMP%\vs_BuildTools.exe" https://aka.ms/vs/17/release/vs_BuildTools.exe || exit /b 1
+            rem 3010 means "installed, reboot pending" and is a success for our purposes.
+            "%TEMP%\vs_BuildTools.exe" --quiet --wait --norestart --nocache ^
+              --add Microsoft.VisualStudio.Workload.VCTools --includeRecommended
+            set "VSEXIT=%ERRORLEVEL%"
+            del "%TEMP%\vs_BuildTools.exe" 2>nul
+            if not "%VSEXIT%"=="0" if not "%VSEXIT%"=="3010" (
+              echo Visual Studio Build Tools installer failed with %VSEXIT%
+              exit /b %VSEXIT%
+            )
+            echo Visual Studio Build Tools installed
+          )
       - name: Install Rust stable
         run: |
           where rustup >nul 2>&1 && (