feat(skills): GitHub PAT support for private skill repos

- Add optional authToken to skill import for GitHub private repos
- Store PAT as encrypted company secret (skill-pat:{skillId})
- Thread auth token through ghFetch and GitHub resolution helpers
- Add PATCH /companies/:companyId/skills/:skillId/auth for managing PAT per skill
- Preserve sourceAuthSecretId across skill re-imports/updates
- Delete PAT secret on PAT clear and on skill deletion to prevent orphans
- UI: Add PAT input field in import form for GitHub URLs
- UI: Add SkillAuthSection with ShieldCheck icon for viewing/updating/removing PAT

packages/shared/src/validators/company-skill.ts

@@ -68,6 +68,11 @@ export const companySkillUpdateStatusSchema = z.object({
 
 export const companySkillImportSchema = z.object({
   source: z.string().min(1),
+  authToken: z.string().min(1).optional(),
+});
+
+export const companySkillUpdateAuthSchema = z.object({
+  authToken: z.string().min(1).nullable(),
 });
 
 export const companySkillProjectScanRequestSchema = z.object({
@@ -135,3 +140,4 @@ export type CompanySkillImport = z.infer<typeof companySkillImportSchema>;
 export type CompanySkillProjectScan = z.infer<typeof companySkillProjectScanRequestSchema>;
 export type CompanySkillCreate = z.infer<typeof companySkillCreateSchema>;
 export type CompanySkillFileUpdate = z.infer<typeof companySkillFileUpdateSchema>;
+export type CompanySkillUpdateAuth = z.infer<typeof companySkillUpdateAuthSchema>;