feat: add fluxer upstream source and self-hosting documentation

- Clone of github.com/fluxerapp/fluxer (official upstream)
- SELF_HOSTING.md: full VM rebuild procedure, architecture overview,
  service reference, step-by-step setup, troubleshooting, seattle reference
- dev/.env.example: all env vars with secrets redacted and generation instructions
- dev/livekit.yaml: LiveKit config template with placeholder keys
- fluxer-seattle/: existing seattle deployment setup scripts

fluxer/packages/api/src/admin/services/guild/AdminGuildVanityService.tsx

@@ -0,0 +1,108 @@
+/*
+ * Copyright (C) 2026 Fluxer Contributors
+ *
+ * This file is part of Fluxer.
+ *
+ * Fluxer is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU Affero General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * Fluxer is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU Affero General Public License for more details.
+ *
+ * You should have received a copy of the GNU Affero General Public License
+ * along with Fluxer. If not, see <https://www.gnu.org/licenses/>.
+ */
+
+import {mapGuildToAdminResponse} from '@fluxer/api/src/admin/models/GuildTypes';
+import type {AdminAuditService} from '@fluxer/api/src/admin/services/AdminAuditService';
+import type {AdminGuildUpdatePropagator} from '@fluxer/api/src/admin/services/guild/AdminGuildUpdatePropagator';
+import {
+	createGuildID,
+	createInviteCode,
+	createVanityURLCode,
+	type UserID,
+	vanityCodeToInviteCode,
+} from '@fluxer/api/src/BrandedTypes';
+import type {IGuildRepositoryAggregate} from '@fluxer/api/src/guild/repositories/IGuildRepositoryAggregate';
+import type {InviteRepository} from '@fluxer/api/src/invite/InviteRepository';
+import {InviteTypes} from '@fluxer/constants/src/ChannelConstants';
+import {ValidationErrorCodes} from '@fluxer/constants/src/ValidationErrorCodes';
+import {InputValidationError} from '@fluxer/errors/src/domains/core/InputValidationError';
+import {UnknownGuildError} from '@fluxer/errors/src/domains/guild/UnknownGuildError';
+import type {UpdateGuildVanityRequest} from '@fluxer/schema/src/domains/admin/AdminGuildSchemas';
+
+interface AdminGuildVanityServiceDeps {
+	guildRepository: IGuildRepositoryAggregate;
+	inviteRepository: InviteRepository;
+	auditService: AdminAuditService;
+	updatePropagator: AdminGuildUpdatePropagator;
+}
+
+export class AdminGuildVanityService {
+	constructor(private readonly deps: AdminGuildVanityServiceDeps) {}
+
+	async updateGuildVanity(data: UpdateGuildVanityRequest, adminUserId: UserID, auditLogReason: string | null) {
+		const {guildRepository, inviteRepository, auditService, updatePropagator} = this.deps;
+		const guildId = createGuildID(data.guild_id);
+		const guild = await guildRepository.findUnique(guildId);
+		if (!guild) {
+			throw new UnknownGuildError();
+		}
+
+		const oldVanity = guild.vanityUrlCode;
+		const guildRow = guild.toRow();
+
+		if (data.vanity_url_code) {
+			const inviteCode = createInviteCode(data.vanity_url_code);
+			const existingInvite = await inviteRepository.findUnique(inviteCode);
+			if (existingInvite) {
+				throw InputValidationError.fromCode('vanity_url_code', ValidationErrorCodes.THIS_VANITY_URL_IS_ALREADY_TAKEN);
+			}
+
+			if (oldVanity) {
+				await inviteRepository.delete(vanityCodeToInviteCode(oldVanity));
+			}
+
+			await inviteRepository.create({
+				code: inviteCode,
+				type: InviteTypes.GUILD,
+				guild_id: guildId,
+				channel_id: null,
+				inviter_id: null,
+				uses: 0,
+				max_uses: 0,
+				max_age: 0,
+				temporary: false,
+			});
+		} else if (oldVanity) {
+			await inviteRepository.delete(vanityCodeToInviteCode(oldVanity));
+		}
+
+		const updatedGuild = await guildRepository.upsert({
+			...guildRow,
+			vanity_url_code: data.vanity_url_code ? createVanityURLCode(data.vanity_url_code) : null,
+		});
+
+		await updatePropagator.dispatchGuildUpdate(guildId, updatedGuild);
+
+		await auditService.createAuditLog({
+			adminUserId,
+			targetType: 'guild',
+			targetId: BigInt(guildId),
+			action: 'update_vanity',
+			auditLogReason,
+			metadata: new Map([
+				['old_vanity', oldVanity ?? ''],
+				['new_vanity', data.vanity_url_code ?? ''],
+			]),
+		});
+
+		return {
+			guild: mapGuildToAdminResponse(updatedGuild),
+		};
+	}
+}