Stage 7: configuration view — backend service, routers, tests, and frontend

- config_service.py: read/write jail config via asyncio.gather, global
  settings, in-process regex validation, log preview via _read_tail_lines
- server_service.py: read/write server settings, flush logs
- config router: 9 endpoints for jail/global config, regex-test,
  logpath management, log preview
- server router: GET/PUT settings, POST flush-logs
- models/config.py expanded with JailConfig, GlobalConfigUpdate,
  LogPreview* models
- 285 tests pass (68 new), ruff clean, mypy clean (44 files)
- Frontend: types/config.ts, api/config.ts, hooks/useConfig.ts,
  ConfigPage.tsx full implementation (Jails accordion editor,
  Global config, Server settings, Regex Tester with preview)
- Fixed pre-existing frontend lint: JSX.Element → React.JSX.Element
  (10 files), void/promise patterns in useServerStatus + useJails,
  no-misused-spread in client.ts, eslint.config.ts self-excluded

backend/app/models/config.py

@@ -5,6 +5,45 @@ Request, response, and domain models for the config router and service.
 
 from pydantic import BaseModel, ConfigDict, Field
 
+# ---------------------------------------------------------------------------
+# Jail configuration models
+# ---------------------------------------------------------------------------
+
+
+class JailConfig(BaseModel):
+    """Configuration snapshot of a single jail (editable fields)."""
+
+    model_config = ConfigDict(strict=True)
+
+    name: str = Field(..., description="Jail name as configured in fail2ban.")
+    ban_time: int = Field(..., description="Ban duration in seconds. -1 for permanent.")
+    max_retry: int = Field(..., ge=1, description="Number of failures before a ban is issued.")
+    find_time: int = Field(..., ge=1, description="Time window (seconds) for counting failures.")
+    fail_regex: list[str] = Field(default_factory=list, description="Failure detection regex patterns.")
+    ignore_regex: list[str] = Field(default_factory=list, description="Regex patterns that bypass the ban logic.")
+    log_paths: list[str] = Field(default_factory=list, description="Monitored log files.")
+    date_pattern: str | None = Field(default=None, description="Custom date pattern for log parsing.")
+    log_encoding: str = Field(default="UTF-8", description="Log file encoding.")
+    backend: str = Field(default="polling", description="Log monitoring backend.")
+    actions: list[str] = Field(default_factory=list, description="Names of actions attached to this jail.")
+
+
+class JailConfigResponse(BaseModel):
+    """Response for ``GET /api/config/jails/{name}``."""
+
+    model_config = ConfigDict(strict=True)
+
+    jail: JailConfig
+
+
+class JailConfigListResponse(BaseModel):
+    """Response for ``GET /api/config/jails``."""
+
+    model_config = ConfigDict(strict=True)
+
+    jails: list[JailConfig] = Field(default_factory=list)
+    total: int = Field(..., ge=0)
+
 
 class JailConfigUpdate(BaseModel):
     """Payload for ``PUT /api/config/jails/{name}``."""
@@ -21,6 +60,11 @@ class JailConfigUpdate(BaseModel):
     enabled: bool | None = Field(default=None)
 
 
+# ---------------------------------------------------------------------------
+# Regex tester models
+# ---------------------------------------------------------------------------
+
+
 class RegexTestRequest(BaseModel):
     """Payload for ``POST /api/config/regex-test``."""
 
@@ -46,6 +90,11 @@ class RegexTestResponse(BaseModel):
     )
 
 
+# ---------------------------------------------------------------------------
+# Global config models
+# ---------------------------------------------------------------------------
+
+
 class GlobalConfigResponse(BaseModel):
     """Response for ``GET /api/config/global``."""
 
@@ -55,3 +104,68 @@ class GlobalConfigResponse(BaseModel):
     log_target: str
     db_purge_age: int = Field(..., description="Seconds after which ban records are purged from the fail2ban DB.")
     db_max_matches: int = Field(..., description="Maximum stored log-line matches per ban record.")
+
+
+class GlobalConfigUpdate(BaseModel):
+    """Payload for ``PUT /api/config/global``."""
+
+    model_config = ConfigDict(strict=True)
+
+    log_level: str | None = Field(
+        default=None,
+        description="Log level: CRITICAL, ERROR, WARNING, NOTICE, INFO, DEBUG.",
+    )
+    log_target: str | None = Field(
+        default=None,
+        description="Log target: STDOUT, STDERR, SYSLOG, SYSTEMD-JOURNAL, or a file path.",
+    )
+    db_purge_age: int | None = Field(default=None, ge=0)
+    db_max_matches: int | None = Field(default=None, ge=0)
+
+
+# ---------------------------------------------------------------------------
+# Log observation / preview models
+# ---------------------------------------------------------------------------
+
+
+class AddLogPathRequest(BaseModel):
+    """Payload for ``POST /api/config/jails/{name}/logpath``."""
+
+    model_config = ConfigDict(strict=True)
+
+    log_path: str = Field(..., description="Absolute path to the log file to monitor.")
+    tail: bool = Field(
+        default=True,
+        description="If true, monitor from current end of file (tail). If false, read from the beginning.",
+    )
+
+
+class LogPreviewRequest(BaseModel):
+    """Payload for ``POST /api/config/preview-log``."""
+
+    model_config = ConfigDict(strict=True)
+
+    log_path: str = Field(..., description="Absolute path to the log file to preview.")
+    fail_regex: str = Field(..., description="Regex pattern to test against log lines.")
+    num_lines: int = Field(default=200, ge=1, le=5000, description="Number of lines to read from the end of the file.")
+
+
+class LogPreviewLine(BaseModel):
+    """A single log line with match information."""
+
+    model_config = ConfigDict(strict=True)
+
+    line: str
+    matched: bool
+    groups: list[str] = Field(default_factory=list)
+
+
+class LogPreviewResponse(BaseModel):
+    """Response for ``POST /api/config/preview-log``."""
+
+    model_config = ConfigDict(strict=True)
+
+    lines: list[LogPreviewLine] = Field(default_factory=list)
+    total_lines: int = Field(..., ge=0)
+    matched_count: int = Field(..., ge=0)
+    regex_error: str | None = Field(default=None, description="Set if the regex failed to compile.")