refactor: split monolith into 3 microservices (frontend, backend, discord-gateway)

- Extract services into services/{frontend,backend,discord-gateway}
- Create packages/shared/ for shared logger, errors, utils, types
- Setup Modular MVC pattern in backend (controller→service→repository)
- Setup event-driven architecture in discord-gateway with Redis pub/sub
- Move Docker files to infra/docker/ with per-service Dockerfiles
- Update docker-compose.yml to use Traefik-only routing (no port exposes)
- Update GitHub Actions deploy workflow for multi-service matrix build
- Fix all import paths and resolve type errors across all services
- All 3 services pass tsc --noEmit clean

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

services/discord-gateway/src/modules/ai-moderation/conversationContext.ts

@@ -0,0 +1,77 @@
+import { formatModerationTextEvidenceForPrompt } from "./indonesianTextNormalizer.js";
+import { formatMediaEvidenceForPrompt } from "../message-capture/messageMetadata.js";
+import type { MessageRecord } from "../message-capture/types.js";
+
+export interface ConversationContextInput {
+  contextBefore: MessageRecord[];
+  targets: MessageRecord[];
+  maxTokens: number;
+}
+
+/**
+ * Formats a timestamp to ISO 8601 string
+ */
+function formatTimestamp(ms: number): string {
+  return new Date(ms).toISOString();
+}
+
+/**
+ * Estimates token count for a string (pessimistic approximation for Indonesian slang & JSON overhead)
+ */
+export function estimateTokens(text: string): number {
+  return Math.ceil(text.length / 3) + 15;
+}
+
+/**
+ * Formats a single message for context or target display
+ */
+export async function formatMessageForPrompt(
+  msg: MessageRecord,
+  label: "context" | "target",
+): Promise<string> {
+  const content = msg.edited_content ?? msg.content;
+  const timestamp = formatTimestamp(msg.created_at);
+  const textEvidence = await formatModerationTextEvidenceForPrompt(content);
+  const textSuffix = textEvidence ? ` ${textEvidence}` : "";
+  const mediaEvidence = formatMediaEvidenceForPrompt(msg.metadata);
+  const mediaSuffix = mediaEvidence ? ` ${mediaEvidence}` : "";
+  return `[${label}] id=${msg.id} time=${timestamp} user=${msg.username}: ${content}${textSuffix}${mediaSuffix}`;
+}
+
+/**
+ * Builds conversation historical context without including targets.
+ * Calculates how much token budget targets use, and fills the rest with context.
+ */
+export async function buildConversationContext(
+  input: ConversationContextInput,
+): Promise<string[]> {
+  const { contextBefore, targets, maxTokens } = input;
+
+  // Calculate tokens used by targets (parallel)
+  const targetLines = await Promise.all(
+    targets.map((msg) => formatMessageForPrompt(msg, "target")),
+  );
+  let usedTokens = targetLines.reduce(
+    (sum, line) => sum + estimateTokens(line),
+    0,
+  );
+
+  const contextLines = await Promise.all(
+    contextBefore.map((msg) => formatMessageForPrompt(msg, "context")),
+  );
+  const selectedContextLines: string[] = [];
+
+  // Go backwards through context, taking most recent first
+  for (let i = contextLines.length - 1; i >= 0; i--) {
+    const line = contextLines[i];
+    const lineTokens = estimateTokens(line);
+
+    if (usedTokens + lineTokens <= maxTokens) {
+      // Unshift so oldest context is first in the array
+      selectedContextLines.unshift(line);
+      usedTokens += lineTokens;
+    }
+  }
+
+  return selectedContextLines;
+}