Refactor config to use test_default

Introduced a `test_default` method to `Config` to provide sane defaults
for integration tests. This refactors several test files to use this new
method, reducing boilerplate and improving maintainability.

Added `LLM_TIMEOUT_SECONDS` to the environment variables and `Config`
struct.

server/src/config.rs

@@ -52,6 +52,7 @@ pub struct Config {
     pub llm_api_key: String,
     pub llm_model: String,
     pub llm_temperature: f32,
+    pub llm_timeout_seconds: u64,
     pub session_timeout_hours: u32,
     /// Whether to set the `Secure` flag on the session cookie. Default `true`.
     /// Set `COOKIE_SECURE=false` only for plain-HTTP local development —
@@ -85,10 +86,59 @@ impl Config {
             llm_api_key: optional_env("LLM_API_KEY", ""),
             llm_model: optional_env("LLM_MODEL", ""),
             llm_temperature: optional_env_parsed("LLM_TEMPERATURE", 0.0),
+            llm_timeout_seconds: optional_env_parsed("LLM_TIMEOUT_SECONDS", 180),
             session_timeout_hours: optional_env_parsed("SESSION_TIMEOUT_HOURS", 8),
             cookie_secure: optional_env_parsed("COOKIE_SECURE", true),
         }
     }
+
+    /// True iff all three required fields for the external analysis LLM are
+    /// non-empty. Used to gate the "Fall abschließen" UI and handler — if
+    /// no LLM is configured, the close action must not be reachable.
+    pub fn llm_configured(&self) -> bool {
+        !self.llm_url.is_empty() && !self.llm_api_key.is_empty() && !self.llm_model.is_empty()
+    }
+
+    /// Sane defaults for integration tests. Not a `Default` impl on purpose:
+    /// production code must go through `from_env()`, and `Default::default()`
+    /// carries an implicit "safe fallback" connotation this value does not
+    /// satisfy (empty users, `/tmp` paths). Override fields via
+    /// struct-update syntax:
+    ///
+    /// ```ignore
+    /// let cfg = Config {
+    ///     data_path: tmp_dir,
+    ///     users: vec![my_user],
+    ///     ..Config::test_default()
+    /// };
+    /// ```
+    #[doc(hidden)]
+    pub fn test_default() -> Self {
+        Self {
+            server_port: 3000,
+            data_path: PathBuf::from("/tmp"),
+            log_level: "info".into(),
+            log_path: PathBuf::from("/tmp"),
+            log_max_days: 90,
+            users: Vec::new(),
+            api_keys: HashMap::new(),
+            retention_audio_days: 30,
+            retention_transcript_days: 30,
+            retention_document_days: 0,
+            whisper_url: "http://localhost:10300".into(),
+            whisper_timeout_seconds: 120,
+            ollama_url: "http://localhost:11434".into(),
+            ollama_model: "gemma3:4b".into(),
+            ollama_keep_alive: 0,
+            llm_url: String::new(),
+            llm_api_key: String::new(),
+            llm_model: String::new(),
+            llm_temperature: 0.0,
+            llm_timeout_seconds: 180,
+            session_timeout_hours: 8,
+            cookie_secure: false,
+        }
+    }
 }
 
 /// Load users from a TOML file and build the API key lookup map.