chore(log): cap container log growth and echo the resolved config

P2 of the logging plan (the README recipe landed with the code change):

- `docker-compose.yml.example`: one `x-logging` anchor applied to all three
  services. json-file grows without limit by default, so a long-running bot
  and the proxy in front of it fill the disk; capped at 10m × 3 files.
- The startup `config:` line now reports what the process actually resolved —
  the state DB path (a mistyped `DATA_DIR` or a surprising CWD was invisible
  until it bit), both TTLs, the caption-quote setting (`off` rather than a bare
  `0`) and whether a proxy is configured. The proxy URL is never printed (it
  may embed credentials) and admin ids — chat identifiers — stay at `debug`.

Verified: `docker compose config -q` accepts the file, and a scripted fake-API
run shows `caption quote off` / `link cache TTL 3600s` under overrides,
`proxy=yes` with no credential in any line, and the ids at `debug` only.

crates/xmedia-bot/src/handlers/mod.rs

@@ -15,6 +15,8 @@ mod urls;
 pub use callback::callback_query_handler;
 pub use commands::register_commands;
 pub use inline::inline_query_handler;
+/// The resolved `$DATA_DIR/task_queue.db` path, for the startup config line.
+pub(crate) use statics::db_path;
 pub use statics::{CHAT_STORE, CONFIG, LINK_CACHE, TASK_QUEUE};
 pub use urls::{start_url_workers, stop_url_workers};
 

crates/xmedia-bot/src/handlers/statics.rs

@@ -23,8 +23,9 @@ static DB: LazyLock<Arc<db::DbPool>> = LazyLock::new(|| {
 /// create parent dirs, so the old hardcoded `data/task_queue.db` failed with
 /// a confusing error when started from a directory without `data/`, and a
 /// CWD-relative path is a footgun for systemd / cron deployments — `DATA_DIR`
-/// lets them pin the state anywhere.
-fn db_path() -> std::path::PathBuf {
+/// lets them pin the state anywhere. Also read by the startup config line, so
+/// the log says where the state actually landed.
+pub(crate) fn db_path() -> std::path::PathBuf {
     let dir = std::env::var("DATA_DIR").unwrap_or_else(|_| "data".to_string());
     let dir_path = std::path::Path::new(&dir);
     std::fs::create_dir_all(dir_path).expect("failed to create data directory");

crates/xmedia-bot/src/main.rs

@@ -67,11 +67,27 @@ async fn main() {
         log::warn!("failed to register commands: {e}");
     }
 
+    // The effective tunables, so an operator can see what the process actually
+    // resolved (a mistyped DATA_DIR or a forgotten TTL override is otherwise
+    // invisible until it bites). The proxy URL is never printed — it may embed
+    // credentials — and admin ids are chat identifiers, so they stay at debug.
+    let quote_chars = match CONFIG.caption_quote_text_chars {
+        0 => "off".to_string(),
+        n => format!("{n} chars"),
+    };
     log::info!(
-        "config: {} admin(s), edit-message TTL {}s",
+        "config: {} admin(s), state {}, edit-message TTL {}s, link cache TTL {}s, caption quote {quote_chars}, proxy={}",
         CONFIG.admin_ids.len(),
-        CONFIG.edit_message_ttl.as_secs()
+        crate::handlers::db_path().display(),
+        CONFIG.edit_message_ttl.as_secs(),
+        CONFIG.link_cache_ttl.as_secs(),
+        if std::env::var("TELOXIDE_PROXY").is_ok() {
+            "yes"
+        } else {
+            "no"
+        }
     );
+    log::debug!("config: admin ids {:?}", CONFIG.admin_ids);
 
     // Queue worker: handles typed tasks, dead-letters failed sends to the
     // task's chat. Both closures use the shared context (the queue requires

docker-compose.yml.example

@@ -1,3 +1,12 @@
+# JSON-file logs grow without limit by default: a long-running bot (and the
+# proxy in front of it) will fill the disk. One cap, applied to every service
+# below via the anchor.
+x-logging: &default-logging
+  driver: json-file
+  options:
+    max-size: '10m'
+    max-file: '3'
+
 services:
   nginx-proxy:
     image: nginxproxy/nginx-proxy:1.11.6-alpine
@@ -13,6 +22,7 @@ services:
     labels:
       - 'com.github.nginx-proxy.nginx'
     container_name: nginx-proxy
+    logging: *default-logging
 
   acme-companion:
     image: nginxproxy/acme-companion
@@ -28,6 +38,7 @@ services:
     container_name: acme-companion
     depends_on:
       - nginx-proxy
+    logging: *default-logging
 
   tgxmb:
     image: yoursfunny/telegram-twitter-media-bot:latest
@@ -55,6 +66,7 @@ services:
     depends_on:
       - nginx-proxy
     container_name: tgxmb
+    logging: *default-logging
     # Webhook mode only: the bot listens on WEBHOOK_PORT; nginx-proxy shows
     # 502s while this is down, so surface it to the orchestrator.
     healthcheck: