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/20260608054953_SocialPosting.cs

@@ -0,0 +1,172 @@
+using System;
+using Microsoft.EntityFrameworkCore.Migrations;
+
+#nullable disable
+
+namespace JobsMedical.Web.Migrations
+{
+    /// <inheritdoc />
+    public partial class SocialPosting : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.AddColumn<string>(
+                name: "InstagramHashtags",
+                table: "AppSettings",
+                type: "character varying(1000)",
+                maxLength: 1000,
+                nullable: true);
+
+            migrationBuilder.AddColumn<string>(
+                name: "SocialBaleBotToken",
+                table: "AppSettings",
+                type: "character varying(200)",
+                maxLength: 200,
+                nullable: true);
+
+            migrationBuilder.AddColumn<string>(
+                name: "SocialBaleChatId",
+                table: "AppSettings",
+                type: "character varying(120)",
+                maxLength: 120,
+                nullable: true);
+
+            migrationBuilder.AddColumn<bool>(
+                name: "SocialBaleEnabled",
+                table: "AppSettings",
+                type: "boolean",
+                nullable: false,
+                defaultValue: false);
+
+            migrationBuilder.AddColumn<bool>(
+                name: "SocialEnabled",
+                table: "AppSettings",
+                type: "boolean",
+                nullable: false,
+                defaultValue: false);
+
+            migrationBuilder.AddColumn<string>(
+                name: "SocialFooter",
+                table: "AppSettings",
+                type: "character varying(1000)",
+                maxLength: 1000,
+                nullable: true);
+
+            migrationBuilder.AddColumn<string>(
+                name: "SocialHeader",
+                table: "AppSettings",
+                type: "character varying(1000)",
+                maxLength: 1000,
+                nullable: true);
+
+            migrationBuilder.AddColumn<bool>(
+                name: "SocialInstagramEnabled",
+                table: "AppSettings",
+                type: "boolean",
+                nullable: false,
+                defaultValue: false);
+
+            migrationBuilder.AddColumn<DateTime>(
+                name: "SocialLastPostedAt",
+                table: "AppSettings",
+                type: "timestamp with time zone",
+                nullable: true);
+
+            migrationBuilder.AddColumn<int>(
+                name: "SocialPostsPerDay",
+                table: "AppSettings",
+                type: "integer",
+                nullable: false,
+                defaultValue: 0);
+
+            migrationBuilder.AddColumn<string>(
+                name: "SocialTelegramBotToken",
+                table: "AppSettings",
+                type: "character varying(200)",
+                maxLength: 200,
+                nullable: true);
+
+            migrationBuilder.AddColumn<string>(
+                name: "SocialTelegramChatId",
+                table: "AppSettings",
+                type: "character varying(120)",
+                maxLength: 120,
+                nullable: true);
+
+            migrationBuilder.AddColumn<bool>(
+                name: "SocialTelegramEnabled",
+                table: "AppSettings",
+                type: "boolean",
+                nullable: false,
+                defaultValue: false);
+
+            migrationBuilder.AddColumn<bool>(
+                name: "SocialUseProxy",
+                table: "AppSettings",
+                type: "boolean",
+                nullable: false,
+                defaultValue: false);
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropColumn(
+                name: "InstagramHashtags",
+                table: "AppSettings");
+
+            migrationBuilder.DropColumn(
+                name: "SocialBaleBotToken",
+                table: "AppSettings");
+
+            migrationBuilder.DropColumn(
+                name: "SocialBaleChatId",
+                table: "AppSettings");
+
+            migrationBuilder.DropColumn(
+                name: "SocialBaleEnabled",
+                table: "AppSettings");
+
+            migrationBuilder.DropColumn(
+                name: "SocialEnabled",
+                table: "AppSettings");
+
+            migrationBuilder.DropColumn(
+                name: "SocialFooter",
+                table: "AppSettings");
+
+            migrationBuilder.DropColumn(
+                name: "SocialHeader",
+                table: "AppSettings");
+
+            migrationBuilder.DropColumn(
+                name: "SocialInstagramEnabled",
+                table: "AppSettings");
+
+            migrationBuilder.DropColumn(
+                name: "SocialLastPostedAt",
+                table: "AppSettings");
+
+            migrationBuilder.DropColumn(
+                name: "SocialPostsPerDay",
+                table: "AppSettings");
+
+            migrationBuilder.DropColumn(
+                name: "SocialTelegramBotToken",
+                table: "AppSettings");
+
+            migrationBuilder.DropColumn(
+                name: "SocialTelegramChatId",
+                table: "AppSettings");
+
+            migrationBuilder.DropColumn(
+                name: "SocialTelegramEnabled",
+                table: "AppSettings");
+
+            migrationBuilder.DropColumn(
+                name: "SocialUseProxy",
+                table: "AppSettings");
+        }
+    }
+}