feat(phase-2): Complete social media API integration

- Add ImageUploadService for public URL generation (Meta APIs)
- Create PublisherManager for unified multi-platform publishing
- Add /api/publish endpoints (single, multiple, thread, test)
- Add compose page in dashboard for creating posts
- Add connection test script (scripts/test_connections.py)
- Update navigation with compose link and logout

New endpoints:
- POST /api/publish/single - Publish to one platform
- POST /api/publish/multiple - Publish to multiple platforms
- POST /api/publish/thread - Publish thread (X/Threads)
- GET /api/publish/test - Test all API connections
- GET /api/publish/platforms - List available platforms

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

app/main.py

@@ -11,7 +11,7 @@ from fastapi import FastAPI
 from fastapi.staticfiles import StaticFiles
 from fastapi.middleware.cors import CORSMiddleware
 
-from app.api.routes import posts, products, services, calendar, dashboard, interactions, auth
+from app.api.routes import posts, products, services, calendar, dashboard, interactions, auth, publish
 from app.core.config import settings
 from app.core.database import engine
 from app.models import Base
@@ -49,6 +49,11 @@ app.add_middleware(
 # Montar archivos estáticos
 app.mount("/static", StaticFiles(directory="dashboard/static"), name="static")
 
+# Montar directorio de uploads para imágenes públicas
+import os
+os.makedirs("uploads/images", exist_ok=True)
+app.mount("/uploads", StaticFiles(directory="uploads"), name="uploads")
+
 # Registrar rutas
 app.include_router(auth.router, prefix="", tags=["Auth"])
 app.include_router(dashboard.router, prefix="", tags=["Dashboard"])
@@ -57,6 +62,7 @@ app.include_router(products.router, prefix="/api/products", tags=["Products"])
 app.include_router(services.router, prefix="/api/services", tags=["Services"])
 app.include_router(calendar.router, prefix="/api/calendar", tags=["Calendar"])
 app.include_router(interactions.router, prefix="/api/interactions", tags=["Interactions"])
+app.include_router(publish.router, prefix="/api/publish", tags=["Publish"])
 
 
 @app.get("/api/health")