feat(skills): support Gitea/Forgejo git hosts end-to-end

The skills source pipeline was hardcoded to GitHub conventions, so even
though the UI now accepts non-GitHub URLs, the server couldn't actually
fetch from anywhere else.

- github-fetch.ts: dispatch by host family (github.com → GitHub API +
  raw.githubusercontent.com; everything else → Gitea/Forgejo API v1 +
  /api/v1/repos/.../media for raw content).
- parseGitHubSourceUrl: also accept Gitea/Forgejo web URLs
  (/{owner}/{repo}/src/{branch|commit|tag}/{ref}/{path}).
- routes/company-skills.ts: drop the hostname='github.com' gate in
  deriveTrackedSkillRef so non-GitHub skills are still tracked.
- Generalize user-facing strings ('GitHub PAT' → 'PAT', 'GitHub source URL'
  → 'Source URL', etc.).

GitHub Enterprise (was assumed by '/api/v3') is no longer a special case —
non-github.com hosts are treated as Gitea/Forgejo. If GHE support is needed
later, add a per-source host-family override.

server/src/services/github-fetch.ts

@@ -1,19 +1,25 @@
 import { unprocessable } from "../errors.js";
 
-function isGitHubDotCom(hostname: string) {
+export type GitHostFamily = "github" | "gitea";
+
+export function inferGitHostFamily(hostname: string): GitHostFamily {
   const h = hostname.toLowerCase();
-  return h === "github.com" || h === "www.github.com";
+  if (h === "github.com" || h === "www.github.com") return "github";
+  return "gitea";
 }
 
 export function gitHubApiBase(hostname: string) {
-  return isGitHubDotCom(hostname) ? "https://api.github.com" : `https://${hostname}/api/v3`;
+  return inferGitHostFamily(hostname) === "github"
+    ? "https://api.github.com"
+    : `https://${hostname}/api/v1`;
 }
 
 export function resolveRawGitHubUrl(hostname: string, owner: string, repo: string, ref: string, filePath: string) {
   const p = filePath.replace(/^\/+/, "");
-  return isGitHubDotCom(hostname)
-    ? `https://raw.githubusercontent.com/${owner}/${repo}/${ref}/${p}`
-    : `https://${hostname}/raw/${owner}/${repo}/${ref}/${p}`;
+  if (inferGitHostFamily(hostname) === "github") {
+    return `https://raw.githubusercontent.com/${owner}/${repo}/${ref}/${p}`;
+  }
+  return `https://${hostname}/api/v1/repos/${owner}/${repo}/media/${p}?ref=${encodeURIComponent(ref)}`;
 }
 
 export async function ghFetch(url: string, init?: RequestInit, authToken?: string): Promise<Response> {
@@ -24,6 +30,9 @@ export async function ghFetch(url: string, init?: RequestInit, authToken?: strin
   try {
     return await fetch(url, { ...init, headers, redirect: authToken ? "manual" : "follow" });
   } catch {
-    throw unprocessable(`Could not connect to ${new URL(url).hostname} — ensure the URL points to a GitHub or GitHub Enterprise instance`);
+    const hostname = (() => {
+      try { return new URL(url).hostname; } catch { return url; }
+    })();
+    throw unprocessable(`Could not connect to ${hostname}`);
   }
 }