feat(web,ui): per-project git provider API base URL overrides

Per provider (github|gitlab|gitea) a project override stored in
~/.config/openchamber/projects/<projectId>.json under gitProviders wins
over the global settings.json value (precedence: project override > global
> built-in default). Server forge routes resolve the override per request
directory (worktree-aware via git-common-dir + containment + path fallback,
60s TTL cache); the override host is also accepted for remote parsing and
client detection. New GET/PUT /api/projects/:projectId/git-providers route;
client openchamberConfig preserves the server-owned gitProviders key;
Projects page gains a Git provider API base URLs section; detection store
hydrates per-project overrides (memory-only, server-authoritative).

packages/web/server/lib/gitlab/repo.js

@@ -1,5 +1,6 @@
 import { getRemoteUrl } from '../git/index.js';
 import { getGitLabAuthAccounts, normalizeBaseUrl } from './auth.js';
+import { getEffectiveProviderApiBaseUrl } from '../git-providers/project-config.js';
 
 // When no explicit host allowlist is provided, accept gitlab.com or any host
 // that matches the base URL of a stored GitLab account. Never github.com.
@@ -115,8 +116,23 @@ export async function resolveGitLabRepoFromDirectory(directory, remoteName = 'or
   if (!remoteUrl) {
     return { repo: null, remoteUrl: null };
   }
+  // A per-project API base override makes its host acceptable for directory
+  // resolution even when no connected account covers it.
+  const overrideBaseUrl = getEffectiveProviderApiBaseUrl('gitlab', directory);
+  let knownHosts;
+  if (overrideBaseUrl) {
+    knownHosts = acceptedHosts();
+    try {
+      const host = new URL(overrideBaseUrl).hostname.toLowerCase();
+      if (host) {
+        knownHosts.add(host);
+      }
+    } catch {
+      // ignore a malformed override base URL
+    }
+  }
   return {
-    repo: parseGitLabRemoteUrl(remoteUrl),
+    repo: parseGitLabRemoteUrl(remoteUrl, knownHosts),
     remoteUrl,
   };
 }