Social auto-posting (phase 1): daily applicant digest to Telegram/Bale + Instagram caption

Adds a «شبکه‌های اجتماعی» admin section + scheduler that publishes a daily
«کادر آماده‌به‌کار امروز» digest:

- AppSetting: social toggles, posts-per-day, editable header/footer,
  per-channel bot token + chat id (Telegram, Bale), Instagram enable +
  extra hashtags, proxy toggle, last-posted timestamp (+ migration).
- SocialPostService: builds today's talent digest as text, posts to
  Telegram and Bale via their bot sendMessage APIs (proxy-aware), and
  produces an Instagram caption + auto hashtags (role/city based).
- SocialPostWorker: posts N times/day, evenly spaced, self-paced; reads
  settings live so it's togglable without redeploy.
- /Admin/Social: credentials + header/footer + posts/day, live preview of
  today's message, «ارسال اکنون» button, and an Instagram caption pack
  with copy button (semi-automatic — you post the image manually).
- Nav link added.

Telegram/Bale post as TEXT (per request). The Vazirmatn image card for
Instagram is phase 2 (needs SkiaSharp+HarfBuzz + a TTF font).

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

src/JobsMedical.Web/Migrations/AppDbContextModelSnapshot.cs

@@ -99,6 +99,10 @@ namespace JobsMedical.Web.Migrations
                         .HasMaxLength(200)
                         .HasColumnType("character varying(200)");
 
+                    b.Property<string>("InstagramHashtags")
+                        .HasMaxLength(1000)
+                        .HasColumnType("character varying(1000)");
+
                     b.Property<bool>("MedjobsEnabled")
                         .HasColumnType("boolean");
 
@@ -133,6 +137,51 @@ namespace JobsMedical.Web.Migrations
                         .HasMaxLength(100)
                         .HasColumnType("character varying(100)");
 
+                    b.Property<string>("SocialBaleBotToken")
+                        .HasMaxLength(200)
+                        .HasColumnType("character varying(200)");
+
+                    b.Property<string>("SocialBaleChatId")
+                        .HasMaxLength(120)
+                        .HasColumnType("character varying(120)");
+
+                    b.Property<bool>("SocialBaleEnabled")
+                        .HasColumnType("boolean");
+
+                    b.Property<bool>("SocialEnabled")
+                        .HasColumnType("boolean");
+
+                    b.Property<string>("SocialFooter")
+                        .HasMaxLength(1000)
+                        .HasColumnType("character varying(1000)");
+
+                    b.Property<string>("SocialHeader")
+                        .HasMaxLength(1000)
+                        .HasColumnType("character varying(1000)");
+
+                    b.Property<bool>("SocialInstagramEnabled")
+                        .HasColumnType("boolean");
+
+                    b.Property<DateTime?>("SocialLastPostedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<int>("SocialPostsPerDay")
+                        .HasColumnType("integer");
+
+                    b.Property<string>("SocialTelegramBotToken")
+                        .HasMaxLength(200)
+                        .HasColumnType("character varying(200)");
+
+                    b.Property<string>("SocialTelegramChatId")
+                        .HasMaxLength(120)
+                        .HasColumnType("character varying(120)");
+
+                    b.Property<bool>("SocialTelegramEnabled")
+                        .HasColumnType("boolean");
+
+                    b.Property<bool>("SocialUseProxy")
+                        .HasColumnType("boolean");
+
                     b.Property<string>("TelegramChannels")
                         .HasMaxLength(2000)
                         .HasColumnType("character varying(2000)");