feat(admin): runtime-editable crawler & analysis config in the dashboard

Move crawler and analysis configuration out of boot-only env vars and into
a DB-backed, admin-editable surface applied live without a restart.

- New `app_settings` table (migration 0026) holds one JSONB row per group;
  env vars seed it on first boot, then the DB is the source of truth.
- `settings.rs` adds serializable Crawler/Analysis DTOs with env-base +
  DB-overlay conversion and field-level validation; env-only/secret fields
  (browser, proxy, TOR, vision API key, PHPSESSID) are never persisted.
- `GET/PUT /api/v1/admin/settings/{crawler,analysis}` (RequireAdmin,
  cookie-only, CSRF-guarded): GET returns the editable DTO + a read-only
  env-managed view + prompt defaults; PUT validates (422 + per-field
  details), persists + audits in one tx, then gracefully respawns the
  affected daemon via a Supervisor.
- AppState swaps the crawler control/resync handles and analysis enable
  gate behind shared runtime cells so reloads take effect with no restart;
  a boot-time spawn failure is logged rather than aborting startup.
- Make the three vision prompts and sampling temperature configurable
  (defaults preserved); cookie_domain is admin-editable too.
- Frontend: tabbed /admin/settings page with grouped fieldsets, prompt
  reset-to-default, env-managed read-only panel, save-&-apply confirm, and
  per-field validation; typed client + ApiError.details.
- Bump version 0.79.1 -> 0.80.0.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/src/config.rs

@@ -90,6 +90,27 @@ impl ResponseFormat {
             _ => ResponseFormat::JsonSchema,
         }
     }
+
+    /// Canonical wire string, the inverse of [`Self::from_str`] for the
+    /// three modes the API exposes.
+    pub fn as_str(self) -> &'static str {
+        match self {
+            ResponseFormat::JsonSchema => "json_schema",
+            ResponseFormat::JsonObject => "json_object",
+            ResponseFormat::None => "none",
+        }
+    }
+
+    /// Parse a wire value, rejecting unknown modes (stricter than
+    /// [`Self::from_str`], which the env loader uses to stay lenient).
+    pub fn parse_strict(s: &str) -> Option<ResponseFormat> {
+        match s.trim().to_lowercase().as_str() {
+            "json_schema" => Some(ResponseFormat::JsonSchema),
+            "json_object" => Some(ResponseFormat::JsonObject),
+            "none" => Some(ResponseFormat::None),
+            _ => None,
+        }
+    }
 }
 
 /// AI content-analysis worker configuration: the enable gate, the local
@@ -146,6 +167,21 @@ pub struct AnalysisConfig {
     /// the repetition loops that otherwise run small models into the token
     /// ceiling. `0` omits the field.
     pub frequency_penalty: f64,
+    /// Sampling `temperature` sent with each request (`ANALYSIS_TEMPERATURE`).
+    /// Defaults to `0.0` (deterministic), which is the most reliable for
+    /// structured JSON output; some models behave better with a small
+    /// positive value.
+    pub temperature: f64,
+    /// System prompt for the single-call (normal-aspect) analysis path
+    /// (`ANALYSIS_SYSTEM_PROMPT`). Defaults to
+    /// [`crate::analysis::prompt::SYSTEM_PROMPT_DEFAULT`].
+    pub system_prompt: String,
+    /// Pass-A OCR-only prompt for tall-page slices (`ANALYSIS_OCR_PROMPT`).
+    /// Defaults to [`crate::analysis::prompt::OCR_PROMPT_DEFAULT`].
+    pub ocr_prompt: String,
+    /// Pass-B grounding prompt — tags/scene/safety (`ANALYSIS_GROUNDING_PROMPT`).
+    /// Defaults to [`crate::analysis::prompt::GROUNDING_PROMPT_DEFAULT`].
+    pub grounding_prompt: String,
 }
 
 impl Default for AnalysisConfig {
@@ -170,6 +206,10 @@ impl Default for AnalysisConfig {
             max_image_bytes: 8 * 1024 * 1024,
             response_format: ResponseFormat::JsonSchema,
             frequency_penalty: 0.3,
+            temperature: 0.0,
+            system_prompt: crate::analysis::prompt::SYSTEM_PROMPT_DEFAULT.to_string(),
+            ocr_prompt: crate::analysis::prompt::OCR_PROMPT_DEFAULT.to_string(),
+            grounding_prompt: crate::analysis::prompt::GROUNDING_PROMPT_DEFAULT.to_string(),
         }
     }
 }
@@ -206,10 +246,23 @@ impl AnalysisConfig {
                 .map(|s| ResponseFormat::from_str(&s))
                 .unwrap_or(d.response_format),
             frequency_penalty: env_f64("ANALYSIS_FREQUENCY_PENALTY", d.frequency_penalty),
+            temperature: env_f64("ANALYSIS_TEMPERATURE", d.temperature),
+            system_prompt: env_prompt("ANALYSIS_SYSTEM_PROMPT", d.system_prompt),
+            ocr_prompt: env_prompt("ANALYSIS_OCR_PROMPT", d.ocr_prompt),
+            grounding_prompt: env_prompt("ANALYSIS_GROUNDING_PROMPT", d.grounding_prompt),
         }
     }
 }
 
+/// Read a prompt override from env, falling back to the default when unset
+/// or blank (so `ANALYSIS_SYSTEM_PROMPT=` doesn't wipe the prompt).
+fn env_prompt(name: &str, default: String) -> String {
+    std::env::var(name)
+        .ok()
+        .filter(|s| !s.trim().is_empty())
+        .unwrap_or(default)
+}
+
 #[derive(Clone, Debug)]
 pub struct Config {
     pub database_url: String,