Add audit log for moderation and admin actions

New audit_log table records actor, action, target and a JSON snapshot
of the details, so entries stay readable after the target is deleted;
the actor is set to NULL when the user is removed. logAudit() is called
from upload delete (single and bulk), comment delete, tag removal, role
create/delete, role permission changes, role assign/revoke and MOTD
updates. Logging failures only warn and never fail the action itself.

The admin page gets an audit card behind the new audit.view permission
with action filter, click-to-filter by user, readable summaries per
action and server-side pagination. Action catalog lives in
shared/utils/audit.ts, labels under admin.auditActions (de/en).

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

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

server/db/migrations/0026_sleepy_colonel_america.sql

@@ -0,0 +1,13 @@
+CREATE TABLE `audit_log` (
+	`id` bigint unsigned AUTO_INCREMENT NOT NULL,
+	`user_id` bigint unsigned,
+	`action` varchar(50) NOT NULL,
+	`target_type` varchar(32),
+	`target_id` varchar(64),
+	`details` json,
+	`created_at` timestamp NOT NULL DEFAULT (now()),
+	CONSTRAINT `audit_log_id` PRIMARY KEY(`id`)
+);
+--> statement-breakpoint
+ALTER TABLE `audit_log` ADD CONSTRAINT `audit_log_user_id_users_id_fk` FOREIGN KEY (`user_id`) REFERENCES `users`(`id`) ON DELETE set null ON UPDATE no action;--> statement-breakpoint
+CREATE INDEX `audit_log_action_idx` ON `audit_log` (`action`);

server/db/migrations/meta/_journal.json

@@ -183,6 +183,13 @@
       "when": 1791040007768,
       "tag": "0025_rare_william_stryker",
       "breakpoints": true
+    },
+    {
+      "idx": 26,
+      "version": "5",
+      "when": 1791391067859,
+      "tag": "0026_sleepy_colonel_america",
+      "breakpoints": true
     }
   ]
 }