v0.1.0-rc10 Better parsing

✨ Features
- deeplink: Add UUID validation and helpers. Validate UUIDs in both parse
  and build operations with `Resource.Valid()` and `Resource.String()`.
- eisenhower: Add `ParseEisenhower` function to parse "do-now",
  "delegate", or numeric "0"-"4" to Eisenhower quadrants. Includes
  `ErrInvalidEisenhower`.
- Add `String()` methods to enum types `Motivation`, `TaskStatus`, and
  `RelationshipStrength` for consistency.
- relationship: Add `ParseRelationshipStrength` with case-insensitive
  parsing for all 7 values.
- deeplink: Add `ParseDeepLink`/`BuildDeepLink` functions. Introduce
  `Resource` type with 6 constants and allow parsing of
  `lunatask://resource/uuid` or plain UUID.
- motivation: Add `ParseMotivation` function for case-insensitive parsing
  of unknown/must/should/want values.
- status: Add `ParseTaskStatus` function for case-insensitive parsing of
  task status strings. Matches `ParsePriority` pattern.

♻️ Code Refactoring
- Move enum types `Motivation`, `TaskStatus`, `RelationshipStrength` and
  their constants from `types.go` to dedicated files. `types.go` now
  contains only `Source` and `Date`.
- status: Rename 'Started' to 'InProgress' to match Lunatask UI. Wire
  format remains "started" but also accepts "in-progress" as input.
- eisenhower: Extract `Eisenhower` type, constants, and methods from
  `types.go` to `eisenhower.go`. Add `String()` method for human-readable
  quadrant descriptions.
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