Refactor analysis file names

The versioning of analysis input and document files
(`analysis_input_v{N}.json`, `document_v{N}.md`) has been removed. All
analysis inputs will now use `analysis_input.json` and generated
documents will use `document.md`.

This simplifies file management, as there's no longer a need to track
and manage multiple versions of these files within a case directory. The
analysis worker will now overwrite the existing `document.md` if it
exists, ensuring that the latest analysis result is always present. The
`version` field has also been removed from `AnalyzeJob` and
`AnalysisInput`.

server/src/analyze/mod.rs

@@ -8,14 +8,18 @@ pub mod prompt;
 pub mod recovery;
 pub mod worker;
 
-/// A single request to analyze a case. Payload is tiny (path + u32), so the
-/// channel is unbounded — persistence lives in `analysis_input_v{N}.json` on
+/// Single-document-per-case filenames. A re-analysis overwrites the
+/// document in place (handler deletes it first; worker writes the fresh one).
+pub const DOCUMENT_FILE: &str = "document.md";
+pub const ANALYSIS_INPUT_FILE: &str = "analysis_input.json";
+
+/// A single request to analyze a case. Payload is tiny (a path), so the
+/// channel is unbounded — persistence lives in `analysis_input.json` on
 /// disk, not in the queue. Recovery re-enqueues any inputs the server may
 /// have held at crash time.
 #[derive(Debug, Clone)]
 pub struct AnalyzeJob {
     pub case_dir: PathBuf,
-    pub version: u32,
 }
 
 pub type AnalyzeSender = mpsc::UnboundedSender<AnalyzeJob>;
@@ -25,19 +29,14 @@ pub fn channel() -> (AnalyzeSender, AnalyzeReceiver) {
     mpsc::unbounded_channel()
 }
 
-/// Persistent input for a single analysis run. Written by the close-case
-/// handler, consumed by the analyze worker, and left on disk indefinitely as
-/// an audit trail of what was sent to the LLM.
-///
-/// Timestamps are stored as ISO-8601 strings (lexicographic order matches
-/// chronological order, so string comparison is sufficient for the
-/// "Nachtrag" detection the UI needs later).
+/// Persistent input for a single analysis run. Written by the analyze
+/// handler, consumed by the analyze worker, removed after a successful
+/// document write.
 #[derive(Debug, Serialize, Deserialize)]
 pub struct AnalysisInput {
-    pub version: u32,
     /// Latest filesystem mtime (server clock) of any `.m4a` in the case at
-    /// the moment the close button was clicked. Used later to detect late
-    /// arrivals that should trigger a re-analysis prompt.
+    /// the moment the analyze button was clicked. Carried through for
+    /// diagnostics / future "Nachtrag" detection.
     pub last_recording_mtime: String,
     pub recordings: Vec<RecordingInput>,
 }