Platform config templates & Postgres migration recovery

- Added Linux/Windows startup config templates and README
- Updated default paths to FHS-compliant locations
- Improved publish profiles for platform targeting
- Enhanced Postgres migration: auto-recover on 42P07 errors
- Added RecordMigrationAsAppliedAsync for manual migration history
- Improved migration logging and error handling
- Added detailed documentation for config and migration fixes

Jellyfin.Server/startup.json

@@ -0,0 +1,40 @@
+{
+  "_comment": "Jellyfin Startup Configuration - Configure path locations for Jellyfin data, logs, cache, and more.",
+  "_documentation": "See FILE_BASED_STARTUP_CONFIG.md for complete documentation",
+  "_priority": "Command-line options \u003E Environment variables \u003E This file \u003E Defaults",
+  "Paths": {
+    "DataDir": null,
+    "ConfigDir": null,
+    "CacheDir": null,
+    "LogDir": null,
+    "TempDir": null,
+    "WebDir": null
+  },
+  "Examples": {
+    "_comment": "Example configurations below - remove this Examples section when customizing",
+    "Linux": {
+      "DataDir": "/var/lib/jellyfin",
+      "ConfigDir": "/etc/jellyfin",
+      "CacheDir": "/var/cache/jellyfin",
+      "LogDir": "/var/log/jellyfin",
+      "TempDir": "/var/tmp/jellyfin",
+      "WebDir": "/usr/share/jellyfin/web"
+    },
+    "Windows": {
+      "DataDir": "C:\\ProgramData\\Jellyfin\\data",
+      "ConfigDir": "C:\\ProgramData\\Jellyfin\\config",
+      "CacheDir": "D:\\Cache\\Jellyfin",
+      "LogDir": "C:\\ProgramData\\Jellyfin\\logs",
+      "TempDir": "D:\\Temp\\Jellyfin",
+      "WebDir": "C:\\Program Files\\Jellyfin\\web"
+    },
+    "Portable": {
+      "DataDir": "./data",
+      "ConfigDir": "./config",
+      "CacheDir": "./cache",
+      "LogDir": "./logs",
+      "TempDir": "./temp",
+      "WebDir": "./web"
+    }
+  }
+}