feat: Meeting Assistant MVP - Complete implementation

Enterprise Meeting Knowledge Management System with:

Backend (FastAPI):
- Authentication proxy with JWT (pj-auth-api integration)
- MySQL database with 4 tables (users, meetings, conclusions, actions)
- Meeting CRUD with system code generation (C-YYYYMMDD-XX, A-YYYYMMDD-XX)
- Dify LLM integration for AI summarization
- Excel export with openpyxl
- 20 unit tests (all passing)

Client (Electron):
- Login page with company auth
- Meeting list with create/delete
- Meeting detail with real-time transcription
- Editable transcript textarea (single block, easy editing)
- AI summarization with conclusions/action items
- 5-second segment recording (efficient for long meetings)

Sidecar (Python):
- faster-whisper medium model with int8 quantization
- ONNX Runtime VAD (lightweight, ~20MB vs PyTorch ~2GB)
- Chinese punctuation processing
- OpenCC for Traditional Chinese conversion
- Anti-hallucination parameters
- Auto-cleanup of temp audio files

OpenSpec:
- add-meeting-assistant-mvp (47 tasks, archived)
- add-realtime-transcription (29 tasks, archived)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/app/routers/ai.py

@@ -0,0 +1,102 @@
+from fastapi import APIRouter, HTTPException, Depends
+import httpx
+import json
+
+from ..config import settings
+from ..models import SummarizeRequest, SummarizeResponse, ActionItemCreate, TokenPayload
+from .auth import get_current_user
+
+router = APIRouter()
+
+
+@router.post("/ai/summarize", response_model=SummarizeResponse)
+async def summarize_transcript(
+    request: SummarizeRequest, current_user: TokenPayload = Depends(get_current_user)
+):
+    """
+    Send transcript to Dify for AI summarization.
+    Returns structured conclusions and action items.
+    """
+    if not settings.DIFY_API_KEY:
+        raise HTTPException(status_code=503, detail="Dify API not configured")
+
+    async with httpx.AsyncClient() as client:
+        try:
+            response = await client.post(
+                f"{settings.DIFY_API_URL}/chat-messages",
+                headers={
+                    "Authorization": f"Bearer {settings.DIFY_API_KEY}",
+                    "Content-Type": "application/json",
+                },
+                json={
+                    "inputs": {},
+                    "query": request.transcript,
+                    "response_mode": "blocking",
+                    "user": current_user.email,
+                },
+                timeout=120.0,  # Long timeout for LLM processing
+            )
+
+            if response.status_code != 200:
+                raise HTTPException(
+                    status_code=response.status_code,
+                    detail=f"Dify API error: {response.text}",
+                )
+
+            data = response.json()
+            answer = data.get("answer", "")
+
+            # Try to parse structured JSON from Dify response
+            parsed = parse_dify_response(answer)
+
+            return SummarizeResponse(
+                conclusions=parsed["conclusions"],
+                action_items=[
+                    ActionItemCreate(
+                        content=item.get("content", ""),
+                        owner=item.get("owner", ""),
+                        due_date=item.get("due_date"),
+                    )
+                    for item in parsed["action_items"]
+                ],
+            )
+
+        except httpx.TimeoutException:
+            raise HTTPException(
+                status_code=504, detail="Dify API timeout - transcript may be too long"
+            )
+        except httpx.RequestError as e:
+            raise HTTPException(status_code=503, detail=f"Dify API unavailable: {str(e)}")
+
+
+def parse_dify_response(answer: str) -> dict:
+    """
+    Parse Dify response to extract conclusions and action items.
+    Attempts JSON parsing first, then falls back to text parsing.
+    """
+    # Try to find JSON in the response
+    try:
+        # Look for JSON block
+        if "```json" in answer:
+            json_start = answer.index("```json") + 7
+            json_end = answer.index("```", json_start)
+            json_str = answer[json_start:json_end].strip()
+        elif "{" in answer and "}" in answer:
+            # Try to find JSON object
+            json_start = answer.index("{")
+            json_end = answer.rindex("}") + 1
+            json_str = answer[json_start:json_end]
+        else:
+            raise ValueError("No JSON found")
+
+        data = json.loads(json_str)
+        return {
+            "conclusions": data.get("conclusions", []),
+            "action_items": data.get("action_items", []),
+        }
+    except (ValueError, json.JSONDecodeError):
+        # Fallback: return raw answer as single conclusion
+        return {
+            "conclusions": [answer] if answer else [],
+            "action_items": [],
+        }