feat: GPU offload, signup limit, load tests & capacity planning

- Route all AI workloads (Ollama, STT, TTS, Image Gen) to GPU server
  (192.168.178.11) via LAN instead of host.docker.internal
- Upgrade default model to gemma3:12b and max concurrent to 5
- Add daily signup limit service (MAX_DAILY_SIGNUPS env var)
- Add GET /api/v1/auth/signup-status public endpoint
- Add k6 load test suite (web-apps, auth, sync-websocket, ollama)
- Add capacity planning documentation
- Fix: add eslint-config to sveltekit-base and calendar Dockerfiles

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

services/mana-auth/src/services/signup-limit.ts

@@ -0,0 +1,93 @@
+/**
+ * Signup Limit — Daily registration cap ("Organic Growth Gate")
+ *
+ * Limits new registrations per day to protect hardware and
+ * enable organic growth. Uses PostgreSQL security_events table
+ * (no Redis dependency needed).
+ *
+ * Configure via MAX_DAILY_SIGNUPS env var (default: 0 = unlimited).
+ */
+
+import { sql } from 'drizzle-orm';
+import type { Database } from '../db/connection';
+
+export class SignupLimitService {
+	private maxDaily: number;
+
+	constructor(private db: Database) {
+		this.maxDaily = parseInt(process.env.MAX_DAILY_SIGNUPS || '0', 10);
+	}
+
+	/** Check if registration is allowed right now */
+	async checkLimit(): Promise<{
+		allowed: boolean;
+		current: number;
+		limit: number;
+		resetsAt: string;
+	}> {
+		// 0 = unlimited (feature disabled)
+		if (this.maxDaily <= 0) {
+			return { allowed: true, current: 0, limit: 0, resetsAt: '' };
+		}
+
+		const todayCount = await this.getTodayCount();
+		const midnight = new Date();
+		midnight.setHours(24, 0, 0, 0);
+
+		return {
+			allowed: todayCount < this.maxDaily,
+			current: todayCount,
+			limit: this.maxDaily,
+			resetsAt: midnight.toISOString(),
+		};
+	}
+
+	/** Count registrations today (UTC) */
+	private async getTodayCount(): Promise<number> {
+		try {
+			const result = await this.db.execute(
+				sql`SELECT COUNT(*) as count
+				FROM auth.security_events
+				WHERE event_type = 'REGISTER'
+				AND created_at >= CURRENT_DATE
+				AND created_at < CURRENT_DATE + INTERVAL '1 day'`
+			);
+			const row = (result as any)[0];
+			return row ? Number(row.count) : 0;
+		} catch {
+			// On error, allow registration (fail open)
+			return 0;
+		}
+	}
+
+	/** Public status for the signup page */
+	async getStatus(): Promise<{
+		registrationOpen: boolean;
+		spotsRemaining: number | null;
+		totalToday: number;
+		limit: number;
+		resetsAt: string;
+	}> {
+		if (this.maxDaily <= 0) {
+			return {
+				registrationOpen: true,
+				spotsRemaining: null,
+				totalToday: 0,
+				limit: 0,
+				resetsAt: '',
+			};
+		}
+
+		const todayCount = await this.getTodayCount();
+		const midnight = new Date();
+		midnight.setHours(24, 0, 0, 0);
+
+		return {
+			registrationOpen: todayCount < this.maxDaily,
+			spotsRemaining: Math.max(0, this.maxDaily - todayCount),
+			totalToday: todayCount,
+			limit: this.maxDaily,
+			resetsAt: midnight.toISOString(),
+		};
+	}
+}